Elements of natural history, and of chemistry: being the second edition of the elementary lectures on those sciences, first published in 1782, and now greatly enlarged and improved, by the author, M. de Fourcroy ... Translated into English. With occasional notes, and an historical preface, by the translator.

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ELEMENTS

O F

NATURAL HISTORY,

AND OF

CHEMISTRY:

BEING THE SECOND EDITION OF

THE ELEMENTARY LECTURES ON
THOSE SCIENCES,

FIRST PUBLISHED IN 1782,

AND NOW

GREATLY ENLARGED AND IMPROVED,

By the Author, M. D E FOURCROTy

DOCTOR OF THE FACULTY OF MEDICINE AT PARIS,
OF THE ROYAL ACADEMY OF SCIENCES, &C. &C. &C.

TRANSLATED HKTWLEN GLISH.

WITH OCCASIONAL NOTES, AND AN HISTORICAL
PREFACE, BY THE TRANSLATOR;

^

—

.^\

VOL. III.

LONDON

/#

64

HINTED FOR G. G. J. AND J. ROBINSON,

PATER- NOSTBR-ROW.

MDCCLXXXVZin

Cx-aL^i-orA-

( m )
CONTENTS

to VOL. III.

CHAP. IX. Of Bifmuth. Page r
Chap. X. Concerning Nickel. n
Chap. XI. Concerning Manganefe. 22
Chap. XII. Of the Regulus of Anti-
mony. - - 32
Chap. XIII. Concerning Zink. 67
Chap. XIV. Concerning Mercury, 94
Chap. XV. Concerning Tin. 156
Chap. XVI. Concerning Lead. 188
Chap. XVII. Concerning Iron. 216
Chap. XVIII. Concerning Copper. 294
Chap. XIX. Concerning Silver. 326
Chap. XX. Concerning Gold. 355
Chap. XXI. Concerning Platina. 383
Chap. XXII. Concerning Bitumens

in general. - 408

Chap. XXIII. Amber. - - 413

Chap. XXIV. Afphaltos. - 424

Chap. XXV. Jet. - - - 427

Chap. XXVI. Pit Coal. - - 428

Chap. XXVII.' Ambergris. - 434

Chap. XXVIII, Petroleum. - 439

Supplement

i y )

Supplement to the Mineral
Kingdom

Concerning Mineral Waters, and the
Methods of analyzing thenj. Page 443

Elements

IRYL£tiV\L

E 1TE M E N/r S

NATURAL HISTORY

A K D O F

CHEMISTRY.

Continuation of the Third Section of
Mineralogy, or the Hiftory of Com-
buftible Bodies.

CHAP. IX.

Of Bifmuth.

ISMUTH, or tin glafs, is a femi-
metal, of a yellowifh white, very
ponderous, and difpofed in large
plates. It fcarcely yields at all to
the ftrokes of the hammer without breaking
into fmall brilliant pieces, and may even be
beat into powder. By immerfion in water, it
lofes about TV of its weight. It is fufcep-
Vol. III. A tible

2 BISMUTH.

tible of cryftallization, in the form of po-
lygonal pr;fms, which are difpofed in quad-
rangular folids, perfectly fimilar to thofe of
marine fait. It has fcarcely any fmell or
tafte.

Bifmuth is often found native. It is
known by its yellowifh brilliant colour;
its foftnefs, or yielding to the knife; its
laminated texture when broken ; and, more
efpecially, by its very great fufibility. It is
ordinarily crystallized in triangular laminae,
which are placed one over the other fiant-
wife. I am in poffeffion of fpecimens of
this femi-metal, in the form of very regu-
lar o&ahedrons; its gangue is commonly
quartzofe. It is found at Scala, in Neritia,
in Dalecarlia, and at Schneeberg in Ger-
many, i

Many modern mineralogifts doubt the
exiftence of the arfenical ore of bifmuth.
Some of them however affirm that this ore is
chatoyant, and commonly difpofed in fmall
glittering lamina? of a bright grey colour. It
islikewife, according to thefe authors, almoft
always mixed with native bifmuth and co-
balt, whofe reddifh effiorefcence is obferv-
able on the furface of the fpecimens.

The fulphureous ore of bifmuth is of a
whitifh grey, inclining to blue, with point-
ed facets, or acute prifms ; it has the bril-
liancy and colour of lead ore, or galena, and
almoft always exhibits fquare facets ; but it

is

BISMUTH. 3

is never found in fragments truly cubical.
It may be cut with a knife. It is very
rare, and is found at Baftnas in Sweden,
and at Schneeberg in Saxony.

Cronfledt likewife fpeaks of a martial ore
of bifmuth* which he fays is found in large
cuneiform fcales at Koniberg in Norway.

Laftly, bifmuth is fometimes met with in
the calciform ftate. This is in the form of
a granulated efflorefcence, of a gfeenifh
yellow, and never of a red colour, on the
furface of ores of bifmuth. Mr. Kirwan
thinks that the calx of bifmuth is united
with the cretaceous acid. Some mineralo-
gifts affirm, that the native vitriol of bif-
muth is mixed with this calx.

To make an affay of the ore of bifmuth, it
is ufually reckoned fufficient to expofe it to a
Jow degree of heat in a crucible, together
with a certain quantity of reducing flux.
As bifmuth is volatile, the fufion fhould be
made as quickly as poffible; it would in-
deed be better to make this affay in clofo
veffels, as Cramer recommended.

The fmelting of bifmuth in the large
way, is not attended with more difficulty*
A cavity is made in the earth, which is co-
vered with billets of wood placed one on the
other; the wood is fet on fire, and the ors
being broken fmall, is thrown in it. The bif-
muth melts, and runs into the cavity, where
it takes an orbicular form* In other places
A 2 tfae

4 BISMUTH.

the trunk of a pine tree, hollowed into the
form of a gutter, is placed in the earth in
an inclined pofition, and wood laid over it;
the bifmuth is thrown on this combuftible
matter after it is fet on fire : the femi-me-
tal melts, falls into the channel, which con-
ducts it into a cavity made in the earth,
over which the extremity of the trunk is
placed. The bifmuth, thus obtained, is
poured into iron moulds.

Bifmuth is fcarcely at all altered by the
contact of light. It is extremely fufible, and
melts long before the red heat commences. In
clofed vefTels it fublimes without alteration ;
if it be permitted to cool flowly, it cryftal-
lizes in Greek volutes ; it cryftallizes the
moil eafily of any metallic fubftance. Mr.
Brongniart is thefirft chemift, who perfect-
ly fucceeded in producing this cryftalliza-
tion.

If bifmuth be kept in fufion with con-
tact of air, its furface becomes covered with
a pellicle, which changes into an earth of a
greenifh grey, or brown, named calx of
bifmuth. Nineteen drachms of bifmuth
calcined in a capfule of glafs, afforded Mr.
Baume twenty drachms thirty-four grains
of calx. Bifmuth heated to rednefs, burns
with a fmall blue flame, fcarcely fenfible.
Its calx evaporates in the form of a yellow-
ifh fmoke, which condenfes on the furface
of cold bodies, into a powder of the fame

colour,

BISMUTH. 5

colour, called flowers of bifmuth. This
powder owes its volatilization only to the ra-
pidity with which the bifmuth burns ; for
if it be expofed alone to fire, it melts into
a greenifh glafs, without fubliming. Geof-
froy the younger obferved, that the flowers
of bifmuth, which rife thelaft,are of a beau-
tiful yellow, refembling orpiment.

The grey or brown calx, the yellow flow-
ers, and the glafs, are nothing more than
combinations of this femi-metal, with the
bafe of vital air, or the oxigynous principle.
They are not reducible without addition, be-
caufe the adhefion between the two princi-
ples, which compofe them, is very confide-
rable ; but inflammable gas, and all organic
combuffible matters, are capable of decom-
poiing them, and reftoring their metallic
ftate, by feizing the oxigynous principle
with which tjiefe bodies have more affinity
than bifmuth.

Mr. D'Arcet having expofed bifmuth in a
ball of unbaked porcelain, to the heat of
the furnace in which that fubftance is ufual-
ly baked, part of the femi-metal flowed
out through a crack; the portion, which
remained in the veiTel, formed a glafs of a
dirty violet colour, while the bifmuth, melt-
ed in communication with the external air,
was yellowifh. From this facl, and many
pthcrs of a like nature, it appears, that
A 3 glaffes

P BISMUTH.

glaffes made with or without the contact
of air, are different from each other.

Bifmuth becomes tarnifhed a little by ex-
pofure to the air, whitifh ruft being form-
ed on its furface. It is not attacked by
water, neither does it combine with earths ;
but its calx unites with all earthy matters,
and facilitates their fufion : it gives a green-
ifti yellow tinge to glaffes into which it en-
ters.

The acflion of the falino-terreftrial fub-
fiances, and alkalis on this femi-metal, are
not yet known.

Boiling oil of vitriol a<!ts on bifmuth,
partly decompofing it, and fulphureous gas
exhales-. The mafs remaining in the veffel
after the decompofition of a part of the acid
is white -3 that portion which is in {he faline
ftate may be feparated by means of water, from
the other portion which is calcined, and
does not contain any acid: the lixivium, by
evaporation, affords a vitriol of bifmuth,%
in fmall deliquefcent needles. This fait is
decompofable by fire, by the falino-terref-
trial fubftances, by alkalis, and even by water
alone, in large quantities.

The nitrous acid difolves bifmuth with
an aflonifhing rapidity $ or rather this femi-
metal decomppfes the acid, and very quick-
ly takes from it the oxigynous principle ;
the mixture becomes very ftrongly heated,
and emits denfe red vapours. If the com-
bination

BISMUTH. 7

bination be made in the pneumato-che-
mical apparatus, a large quantity of ni-
trous gas is obtained; and this procefs is
one of the readicft and moft convenient for
procuring this gas. During the folution, a
black powder is precipitated, which Lemery
fuppofed to be bitumen, and Pot confidered
as calcined bifmuth ; Mr. Baume fufpected
it to be fulphur.

The nitrous folution of bifmuth is with-
out colour, and when it is much faturat-
ed, it affords cryftals without evaporation.
Evaporation, and Cooling, afford a nitre
of bifmuth ; concerning the form of which
chemifts differ. Mr. Baume affirms, that
this fait is difpofed in large needles, point-
ed at one end. Mr. Sage afferts, that
the cryftals are tetrahcdral prifms, a lit-
tle flattened and terminated by two ob-
tufe trihedral pyramids, whole planes make
one rhombus and two trapeziums. By a flow
evaporation, I have obtained flattened rhom-
boids, very large, and perfectly fimilar to the
calcareous fpar of Iceland.

The nitre of bifmuth detonates feebly,
and with reddifh fcintillations, after which
it melts and fwells up, leaving a calx of a
greenifh yellow, not reducible without addi-
tion. This fait expofed to air, lofes its
tranfparency, at the fame time that the wa-
ter of cryftallization is difiipated. If water
be added, inftead of diflblving it, the fluid
A 4 becomes

3 BISMUTH.

becomes white, milky, and a calx of bif-
muth is precipitated.

The fame thing happens, if the nitrous
folution of bifmuth be poured into water;
the greateft part of the calx of this femi-
metal being precipitated under the form of
a white powder, called magiftery of bif-
muth. One hundred grains of this metal,
diflblved in the nitrous acid, afford one^
hundred and thirteen grains of magiftery,
by reafon of the oxigynous principle with1
which it combines. A large quantity of
water muft be ufed, if the precipitate be
defired very white and fine. It is ufed as a
pigment for rendering the fkin white, but
it has the inconvenience of becoming black,
when in contact with odoriferous or com-
buftible matters. This property is more
evident in this, than in moft of the metallic
calces. Though nitre of bifmuth be in a
great meafure decompofed by water, a por-
tion neverthelefs remains diffolved, which
cannot be precipitated, but by lime or al-
kalis. The character of being precipitat-
ed by water, is common to all the folutions
of bifmuth.

The muriatic acid a&s with difficulty on
this femi-metal. It is neceflary that the
acid fhould be very concentrated, and be
kept in digeftion on the bifmuth for a long
time > the folution fucceeds ftill better,
when a large quantity of marine acid is dif-

tilled

BISMUTH. 9

tilled from the metal. The mixture has
an hepatic fmell ; the refidue is to bei
wafhed with water, which becomes charged
with a portion of the metallic calx united
to the acid. The muriate of bifmuth cry-
stallizes with difficulty ; it may be fublimed
into a kind of butter ; it ftrongly attra&s
the humidity of the air; and laftly, water
decompofes it, and precipitates it in the
form of a white calx.

The action of the other mineral acids on
bifmuth is not known.

Bifmuth is calcined by nitre, but with-
out any fenfible detonation; this femi-me-
tal does not decompofe fal ammoniac, but
its calx completely feparates the volatile al-
kali from this fait. In this experiment a
large quantity of alkaline gas is obtained,
and the refidue is a combination of the me-
tallic calx, with the muriatic acid. If bif-
muth do not aft on the fal-ammoniac, in
confequence of the fmall degree of adlion,
which the muriatic acid has for this femi-
metal ; the property its calx poffefles of de-
compofing this fait, is very remarkable, and
proves that it in fome meafure refembles
faline fubftances.*

* The decompofition of fal ammoniac, by the calx of
bifmuth, agrees with die general tenor of facts, which (hew,
that the calces of metals are more ftrongly acled on by the
muriatic acid, than the metals themfelves : the caufe of this
need not be here infilled on. T.

Inflammable

JO BISMUTH.

Inflammable gas alters the colour of bif-
muth, and gives it a violet tinge.

Sulphur combines with this femi-metal
by fufion, and produces a fort of grey mine-
ral, of a blueiih and brilliant appearance,
which cryftallizes in beautiful tetrahedral
needles, fimilar in colour and appearance to
the fineft fpecimens of antimony.

The aftion of arfenic on bifmuth is not
well known. This femi-metal does not
unite with cobalt, which remains feparate
from it in the fmelting.

Bifmuth is employed by the pewterers,
to communicate hardnefs to tin. It may
be fubftituted inftead of lead, in the art
of cupelling the perfeft metals, becaufe,
like that metal, it has the property of
flowing into a glafs, which is abforbed
by the cupels. Geoffroy the younger has
obferved, and recorded many circumftances
in which this femi-metal refembles lead.
The effedts of bifmuth on the animal (Eco-
nomy can only be conje<ftured ; but there
is reafon to think that its ufe, like that of
lead, would be dangerous; and there are
fome inflances of bad effe&s arifing from the
external ufe of this femi-metal. We have al-
ready obferved, that the calx of bifmuth is
ufed as a pigment for the fkin, and that
#tong fmelling matters alter its colour ;
fuch fmells as are fetid, more particularly
produce this effedh The vicinity of {laugh-
ter^

BISMUTH. II

ter-houfes, of common-fewers, of neceflary-
houfes, and almoft every other ftrong fmell,
has that effedl on this calx, and caufe its
colour to become more or lefs black. The
vapour of liver of fulphur, or the fmell of
eggs, produce this effedt very quickly. A
very common experiment in natural philo-
sophy fhews this property in a ftriking man-
ner. If characters be written with a folution
of bifmuth, on the firft page of a book of
fifty leaves, and the laft page be impregnated
with a fmall quantity of the liquid liver of
fulphur 5 a fhort time afterwards, the hepa-
tic vapour carried by the air, which circu-
lates between all the leaves, arrives at the
other extremity of the book, and converts
the colourlefs charadlers marked on the firft
page into a deep brown. It is affirmed,
that the hepatic gas paffes through the pa-
per; but Mr. Monge has proved, that it is
the air which carries it in this manner, from
one leaf to another, fince the effedt does not
take place, when the leaves are glued to-
gether.

CHAP, X.

Concerning Nickel.

"^ICKEL was confidered by Cronftedt,
•*^ as a peculiar femi-metal, when he firft
made it known in the year 1751, and 17541

in

12 NICKEL.

in the adls of the Academy of Stockholm.
This femi-metal, according to him, is of a
white brilliant colour, tending to red -> es-
pecially at the external furface. It is very
brittle, and in its fra<fture appears to be com-
pofed of facets, which diftinguifh it from
cobalt. Mr. Arvidfon, who, together with
Bergman, has publifhed a thefis on the pro-
perties of nickel, which is tranflated, and
inferted in Rofier's Journal, for Qdtober,
1776, obferves, that nickel obtained by the
roafting and fufion of its ores, as Cronftedt
direfls, is far from being in a ftate of pu-
rity, and that it contains fulphur, arfenic,
cobalt, and iron. As Bergman has fucceed-
ed by a great number of ingenious proceffes,
to deprive it of moft of thefe foreign mat->
ters, and to obtain nickel different from
that of Cronftedt, in many of its properties,
we fhall follow his authority, after having
firft fpoken of its ores.*

Nickel is found united to fulphur and
arfenic. It ores have a coppery red colour,
and are almoft always covered with a green-*
ifh grey efflorefcence. The Germans call
it kupfer-nickel, or falfe copper. This
mineral is very common at Freyberg, in
Saxony, where it is often mixed with the
grey ore of cobalt; but its red colour, and

* This EfTay is printed in the fecond volume of the En*
glifh tranilation of Bergman's EfTays. T.

its'

NICKEL. 13

its greenifh efflorefcence, diftinguifh it from
that ore, which is grey or black, and has
a red efflorefcence. It is often crvftallized
in cubes. Wallerius diftinguifhes the kup-
fer-nickel, by the name of cobalt ore, of a
coppery red ; he thinks it to be a compound
of cobalt, iron and arfenic. Linnaeus con-
fidered it as copper mineralized by arfenic.
Rome de Lifle has arranged it, with Walle-
rius, among the ores of cobalt, and like him,
thinks that it is a compound. Mr. Sage
having treated this ore with fal ammoniac,
obtained iron, copper, and cobalt ; he thinks
that it is compofed of thefe three metallic
matters, together with arfenic. It likewife
contains a fmall proportion of gold, accord-
ing to this chemift. It it proper to ob-
ferve, thefe refults do not agree with thofe
of Bergman ; he is faid to have operated on
the kupfer-nickel of Biber, in HeiTe, and of
Allemont in Dauphiny.

Cronftedt affures us, that the metal-
lic matter called fpeifs by the Germans,
which is collefted in the crucibles ufed in
the melting of fmalt, affords nickel. Mr.
Monnet thinks that the fpeifs, of the manu-
fa<fture of Gengenback, 14 leagues from
Strafburg, is true nickel ; and as the ore of
cobalt made ufe of in that place to make
fmalt, is very pure, he concludes that nickel
is neceffarily a produft of cobalt itfelf, as we
ftiall prefently fee. But Mr. Baume has

obtained

14 NICKEL.

obtained nickel from almoft all the ores of
cobalt by means of fulphur; it therefore
feems that the ore of cobalt, which is
wrought at Gengenback, contains nickel not
diftinguifhable by the eye, on account of the
intimate union of thefe two metallic mat-
ters.

To obtain nickel from the ore, it is flow-
ly roafted, in order to drive off a portion of
the fulphur and arfenic it contains. It is
by this means converted into a greenifh calx.
The greener it is, the greater the quantity of
nickel it contains, according to Bergman
and Arvidfon. It is afterwards melted with
three parts of black flux and marine fait, and
a regulus is by that means obtained, fuch as
Cronftedt fpeaks of, but which is far from
being pure nickel. Its fcoria? are brown or
blue. Many chemifts, fmce the experi-
ments of Arvidfon, ftill continue to think
that this metallic fubftance is a natural al-
loy of iron, cobalt, and arfenic ; as to cop-
per, there is no chemift but Mr. Sage, who
affirms, that he has obtained it from kup-
fer-nickel. Mr. Monnet thinks that nick-
el is cobalt, deprived of iron and arfenic.
In proportion as we (hall proceed in the
examination of the properties of this femi-
xnetal, we fhall perceive the caufes of thefe
different opinions having been adopted.
We think with Bergman, that the extreme
difficulty of obtaining nickel in a ftate of

purity,

NICKEL. 1$

purity, is the circumftance which has de-
ceived the generality of chemifts ; and this
truth is fully proved in the diflertation of
Mr. Arvidfon, already quoted. As it is cer-
tain that this metallic fubftance has very
peculiar properties, however pure it may be
made; and that no means of feparating it by
analyfis into different metallic fubftances, nor
of recompofing it by any mixture, have been
yet difcovered; it ought to be regarded as a
peculiar femi-metal, till further experiments
fhall convince us to the contrary.

The femi-metal which affords, by fimple
fufion, kupfer-nickel, is of a reddifh white,
very brittle, and of a plated texture. It
contains much arfenic, cobalt, and iron.
Mr. Arvidfon fubjefted it to fix calcinati-
on^, each for the fpace of between 6 and
14 hours, and reduced the regulus after
each calcination. During the calcination,
he obferved, that vapours cf arfenic, and
white vapours which have not the fmell of
this femi-metal, were driven off: the powder
of charcoal added in thefe operations, faci-
litated the volatilization of the arfenic. The
nickel, whofe weight was greatly diminil'h-
ed by thefe fix calcinations, ftill had an ar-
fenical fmell, and continued to be attracted
by the magnet. It was then fufed fix times
with lime and borax, and calcined a feventh
time, with the addition of charcoal, till it
no longer fent forth arfenical fumes : this

cal*

l6 NICKEL.

calx was ferruginous, and ftriped with green*
When reduced, it afforded martial ochre,
and a button ftill obedient to the magnet.
Thefe experiments have always fucceeded in
the fame manner, with many fpecimens of
nickel from different countries. Treatment
with fulphur, and liver of fulphur, detonation
with nitre, folution in the nitrous acid, and
in the volatile alkali, made by Mr. Arvidfon,
never deprived nickel of all its iron. From
thefe experiments he concluded, that it is
irnpoffible to purify this femi-metal accu-
rately ; that the fulphur is not feparated but
by repeated calcinations ; that the arfenic
adheres ftill more ftrongly; that it may be
drawn off by the afiiftance of powder of
charcoal, and of nitre ; that cobalt is ftill
more intimately combined with this femi-
metal, fince the nitre fhews its prefence,
though no other indications were before
perceived ; and that it is impofiible to de-
prive it of all the iron it contains, becaufe
when the nickel has been treated in all thefe
various manners, it is fometimes more ftrong-
ly attracted by the magnet than before.
Mr. Arvidfon thinks, from thefe circum-
ftances, that this fubftance is nothing elfe
but iron in a peculiar ftate, and he has
drawn up a comparative view of many of the
properties of cobalt, of loadftone, and of
nickel ; from which he confiders thefe three

metallic

NICKEL. 17

metallic matters as iron differently modi-
fied. But as the principal property of nick-
el, which has led Mr. Arvidfon to this con-
clufion, is its magnetifm ; may we not con-
clude that thefe two metallic fubftances, fo
different in all their other properties, are
not to be confounded together on this ac-
count ? for it has not been proved that mag-
netifm is peculiar to iron, or that it may
not exift in many other metallic fubftan-
ces. I think therefore, that notwithftand-
ing the property of being attracted by the
magnet which nickel poffeffes, it ought to
be confidered, when purified by the pro-
ceffes of Mr. Arvidfon, as a peculiar femi-
metal ; fince it cannot be extracted either
from other metallic fubftances, nor can be
perfectly imitated by any mixture; and laft-
ly, becaufe it poffeffes properties common
to no other metal, as we fhall proceed to
fhew. Mr. Kirwan ha entirely adopted this
opinion in his mineralogy.

Its texture is not plated, as Cronftedt af-
rerted, but granulated, as its fracture fhews.
It is nine times heavier than water. It is
not brittle, but on the contrary, fufficiently
ductile, to make it a queftion with Bergman,
whether he fhould rank it among the me-
tals or femi-metals. It is nearly as diffi-
cult to melt as forged iron, is extremely fix-
ed in the fire, and becomes calcined when
Vol. Ill, B heated

l8 NICKEL.

heated with accefs of air, affording a calx
of a green, which is deeper in proportion to
its purity : it is not known whether this
calx is fufible into glafs. The fluxes and
combuftible matters commonly ufed in re-
ducing the metals, produce their effecT:
with this. The action of air and water on
nickel are not known 3 its calx, when melted
with matters proper to form glafs, gives
them a hyacinthine colour, more or lefs
red. The adtion of lime, magnefia, and the
three pure alkalies, on nickel, are ftill un-
known.

Mr. Sage affirms, that when four parts of
oil of vitriol are diftilled from one part of
the regulus of kupfer-nickel, in powder,
the fulphureous acid paffes over: the refidue
is greyifh, and being diflblved in diftilled
water, produces the moft beautiful green
colour. The cryftals obtained from this
folution are foliated, and of the colour of
an emerald. According to Mr. Arvidfon,
the vitriolic acid forms a green fait, in de-
cahedral cryftals, with the calx of nickel.
Thefe confift of two quadrangular pyra-
mids, united together and truncated near
their bafe.

This calx is eafily foluble in the nitrous
acid, and cryftallizes in rhombic cubes.
According to Mr. Sage, all the other fo-
lutions of nickel, or its calx, either in the
muriatic acid, or in vegetable acids, are
more or lefs green. Fixed alkalis pre-
cipitate

NICKEL. 19

cipitate it of a greenifh white colour, and
re-diffblve it, at which period the liquid
becomes yellowifh. The volatile alkali,
poured into a folution of nickel, produces a
beautiful blue colour; this fait prefents the
fame phenomena, when mixed with the pre-
cipitates of this femi-metal, by fixed alka-
lis. As the folutions of copper exhibit the
fame colour with volatile alkali, which is
efteemed a very proper teft of the prefence
of copper, it has been thought that nickel
contains this metal. Cronftedt, however,
tried in vain all the known methods of ex-
tracting copper from the folution of nickel,
tinged blue by the volatile alkali. This
fait, befides, does not immediately diiTolve
nickel, as it does copper. It is therefore
proved, as Bergman thinks, that the pro-
perty of turning green belongs to nickel
itfelf, and is not owing to the prefence of
copper. This chemift did not obferve any
certain figns cf the folution of nickel, by
the cretaceous acid, in an experiment where
he kept this metal for eight days in w7ater,
impregnated with that acid.

Nickel detonates with nitre ; this detona-
tion afforded Mr. Arvidfon a method of dif-
covering the prefence of cobalt, which no
other proof had rendered fenfible. Nitre
has likewife the property of augmenting the
intenfity of the hyacinthine colour, com-
municated by calx of nickel to glalTes, and
B 2 of

20 NICKEL.

of caufing it to re-appear after it has been
diffipated by heat, as frequently happens
with this calx in glafs, and is common to
it with the femi-metal we fhall next pro-
ceed to examine.

The calx of nickel fufed with borax,
likewife gives it an hyacinthine colour.

It partly decotnpofes fal-ammoniac. The
martial flowers obtained by Mr. Sage, in
this experiment, arofe from his not having
employed a regulus as pure as that of Mr.
Arvidfon -, for this laft chemift allures us,
that the flowers he obtained by folution
were white, and gave no indication of the
prefence of iron, by the teft of nut galls :
a fmall quantity of volatile alkali, and mu-
riatic acid, paffes into the receiver ; the re-
fidue, when reduced, affords nickel partly
deprived of its magnetifm.

The adtion of inflammable gas on nickel
is not yet known.

This femi-metal combines readily by fu-
fion with fulphur, and then forms a kind
of hard mineral, of a yellow colour, with
fmall brilliant plates. When ftrongly heat-
ed in contadt with air, it deflagrates, and
emits very luminous fparks, fimilar to
thofe afforded by iron when forged. Cron-
ftedt, who firfl made this experiment,
did not purfue it ; he obferved only, that
the phenomenon does not take place, if the

contadl

NICKEL. 21

contact of air be prevented, by covering the
metal with glafs in fufion. The fame che-
mift acquaints us, that this fcmi- metal is
foluble in liver of fulphur, and forms a
compound, refembling the ores of copper.
The fulphur cannot be feparated from nick-
el, but by repeated fufions and calcina-
tions.

Nickel combines with arfenic, to which
it has a ftrong attraction. Mr. Monnet (who
at firft, after Cronftedt, confidered nickel
as a peculiar femi-metal) having obferved
that it forms a blue glafs when united to
arfenic, fimilar to that which cobalt affords,
adopted the opinion that nickel is nothing
elfe but cobalt deprived of arfenic and iron.
Mr. Monnet therefore confiders cobalt, as
well as nickel, as metallic mixtures. Berg-
man thinks, that if a blue glafs be obtained,
by the addition of arfenic to nickel, no other
confequence ought to be deduced, than
that it is caufed by the cobalt, which it is
known to contain, and whofe properties
are hidden by the latter, till it is calcined
and feparated from the nicke! by means of
arfenic; at which time its properties, more
efpecially that of flowing into a ^hik, of a
blue tinge, fhew themfelves. We have al-
ready obferved, that nickel cannot be entirely
feparated from arfenic, but by repeated cal-
cinations, with the addition of charcoal in
powder. Nickel unites Hill more intimately
•B 3 to

22 "MANGANESE.

to cobalt than to arfenic, fo that they can-
not be feparated without the greateft diffi-
culty. Cobalt may exift in this combina-
tion, without (hewing any indications of its
principal properties. Nitre, borax, and arfe-
nic, are the only fubftances by which its
prefence can be exhibited in fufion.

Cronftedt affirms, that nickel forms with
bifmuth a brittle and fcaly regulus ; the
folution in the nitrous acid feparates thefe
two femi-metallic fubftances imperfectly,
by virtue of the property which nitre of
bifmuth pofferTes of being decompofed by
water. No ufe has yet been made of nickel.

CHAP. XI,
Concerning Manganefe.

MANGANESE, a grey dark coloured
mineral, which foils the fingers, and
is employed in glafs-houfes in different pro-
portions, either to colour, or to take away
colour from glafs, has been long known by
the name of black magnefia, or manganefe.
Workmen have called it the fope of glafs,
from its property of rendering it colourlefs.
Many naturalifts, judging by its colour,
and the martial earth with which its fur-
face is often covered, have taken it for a
meagre ore of iron. Pott and Cronftedt,

after

MANGANESE. 2$

after- an exact analyfis, did not confider
it as a ferruginous matter. The latter
affirmed, that it contains a fmall proportion
of tin. Mr. Sage reckons it among the
ores of zink, and thinks that it is formed
by the combination of that femi-metal and
cobalt with the muriatic acid; he adds,
from his own trials, that it fometimes con-
tains iron or lead.

The weight of manganefe, its property
of tinging glafs, and of affording a whitifh
precipitate when the phlogifticated alkali is
poured into its folutions, caufed Bergman
to fufpecl, as he acquaints us in the laft
paragraph of his diflertation on the elective
affinities, that this mineral contains a pe-
culiar metallic fubftance. His fufpicion has
been fully confirmed by one of his difciples
Mr. Gahn, doctor in medicine at Stock-
holm, to whom, together with Scheele, we
are indebted for the difcovery of the phof-
phoric acid in bones. This phyfician is the
firft who obtained a regulus of manganefe,
probably by treating it with reducing flux.
The degree of fire neceiTary for this opera-
tion, is, doubtlefs, very great ; for I have
been a witnefs to the attempts of Mr. Brong-
niart, an experienced chemift, who tried in
vain to reduce it in a furnace, which was
capable of producing an excefiive degree of
heat. I have been affured, that the reduc-
tion has been fuccefsfully performed at Pa-

B 4 ris

24 MANGANESE.

ris by employing the flux of Mr. De Mor-
veau, with which this chemift obtained
iron in a very well formed button : but I
think that Mr. De la Peyroufe is much in
the right in his opinion, that fluxes are
pernicious in this operation. I have at-
tempted the reduction in an excellent melt-
ing furnace, conftrudled in the laboratory
of the Veterinarian fchool at Alfort. I have
not yet obtained a perfed: button, but I have
obtained a confiderable quantity of metallic
globules, two or three lines in diameter.
On feveral occasions, when I have employed
fixt alkalis and borax, no metal was reduced.
In my trials, each fmall metallic globule
of manganefe was incrufted with glafs,
or a vitreous frit of a deep colour. Manganefe
ought to be coniidered as a peculiar femi-
metal, becaufe its analyfis has not yet been
made, and it is found to poffefs properties
common to no other metallic fubftance.
Mr. De Morveau, in his tranflation of Berg-
man, calls the regulus, manganefe, and pro-
pofes to call thofe fubftances from which it
is obtained, and in which it exifts in a calci-
form ftate, ores of manganefe. The proper-
ties of this femi-metal have been greatly elu-
cidated by the labours of Bergman, Scheele,
Gahn, Rinman, Engeflroem, Ilfeman and
Peyroufe. It is from the labours of thefe
chemifts, as well as from my own particular
experiments, that I fhall borrow the follow-
ing

MANGANESE. 2$

ing account of this fubftance ; firft obferving,
that the difficulty of reducing the ores of
this femi-metal, is the caufe why we are
much better acquainted with the properties
of its calces, than with thofe of the metal-
lic fubftance itfelf. Mr. Scheele, one of the
firft chemifts of the prefent age, does not
appear to have fucceeded in reducing it,
fince he no where fpeaks of the properties
it pofleffes in the metallic ftate.

The ores of manganefe are known by
their grey, brown, or black colour, more or
lefs brilliant, and likewife by their external
appearance : they may be diftinguifhed into
a confiderable number of varieties.
Variety

1 . Ore of manganefe cryftallized in rhom-

boidal priims, ftriated in the direction
of their length, and feparated from
each other.

2. Cryftallized ore of manganefe, whofe

priims are difpofed in bundles, or
aggregates.

3. Cryftallized ore of manganefe, in

fmall needles, difpofed in the form
of ftars.

4. Efflorefcent ore of manganefe, black

and friable ; it foils the fingers like
foot.

5. Velvet ore of manganefe; thefe arc

very fmall needles, which falling in-
to

26 MANGANESE.

to efflorefcence, have a beautiful dead
black colour, refembling velvet.
6. Compact and amorphous ore of man-
ganefe, of a black grey, often with
cavities, and very heavy ; it foils the
fingers, and is fometimes found in
brilliant needles. The Perigord
ftone belongs to this variety.
j. Spathofe manganefe, found in the iron
mines of Klapperud, at Frefco in
Dalecarlia, and defcribed by Mr.
Rimman.
8, Native manganefe, in metallic globu-
les, found at Sem, in the county of
Foix, by Mr. De la Peyroufe, and
defcribed by him, together with many
varieties of the ores of manganefe,
found at the fame place, in Rozier's
Journal for January 1780.
Mr. Scheele has difcovered the calx of
manganefe in the allies of vegetables, and
attributes the green and blue colour, which
fixt alkali often takes in calcination, to its
prefence. The green colour of the alkali
of tartar treated with lime, and the rofe
colour which I have often obferved in its
combination with acids, arifes, no doubt,
from this metallic calx.

Manganefe, extracted from its ore, is of a
brilliant white; when broken its texture ap-
pears granulated like that of cobalt. It is
hard, and breaks, after being in a fmall de-
gree

MANGANESE. 2J

gree flattened by the hammer. Its infufibility
is greater than that of iron, which at firft
cauied Bergman to conie&ure, that it has
ibme affinity with plati.ia; if it be heated
with contact of air, it is converted into a
calx, at firft whitifh, which becomes more
and more black, in proportion as the cal-
cination proceeds. I have obferved that the
imall globules of manganefe, obtained by
the procefs I have before fpoken of, very
foon change by the contact of air ; they are
tarnifhed, and become of a lilac and violet
colour.

The action of manganefe on earths, and
the falino-terreftrial fubftances, has not yet
been examined ; the calx of this femi-metal
gives a violet or brown colour to glafs, fuf-
ceptible of a great number of modifications,
but eafily deftroyed by the action of com-
buftible fubftances. Scheele has made a
great number of ingenious experiments on
this head.

The manner in which fixed alkalies act on
manganefe, is not known -> but the calx of
this femi-metal combines with the volatile
alkali, and is revived. Bergman obferves,
that in this combination, a peculiar gas is
difengaged, which he regards as one of the
principles of the volatile alkali, but of which
he does not fpeak fully. It appears to be
the atmofpheric mephitis, difcovered to
exift in volatile alkali, by Mr. Berthollet;

and

28 MANGANESE.

and that the inflammable gas of this fub-
ftance, acting on the oxyginous principle
united to manganefe, reduces it to a ftate lefs
perfectly calciform, and of a white colour.

The vitriolic acid diflblves manganefe and
its calces ; this laft folution is coloured, but
becomes clear by the addition of any com-
buftible matter, fuch as fugar or honey. It
affords a tranfparent vitriol in prifmatic
cryftals with parallel fides. If it be diftilled
to drynefs, fulphureous gas is obtained.

The nitrous acid likewife difTolves it,
emitting at the fame time red vapours. Its
calx is not attacked by this acid, unlefs it be
fuming, or fome combuftible body, fuch as
honey or fugar be added. Alkalis precipi-
tate from its foiutions a white calx, foluble
in acids, which, when heated, becomes
black, and is calcined ftill more. Mr. Scheele
thinks that this calx is charged with the
phlogifton of the acid, and obferves, that
in fact, the black calx of manganefe is very
foluble in phlogifticated acids. Bergman
thinks, that this femi-metal has a greater
affinity with falts than mod metallic fub-
fiances ; he places it in his table, near the
top of that column, which contains the
elective attractions of acids.

The muriatic acid likewife difTolves man-
ganefe, which gives it a deep brown colour;
when this folution is heated, the colour dif-

appears ;

MANGANESE, 29

appears : water occafions a precipitate, and
alkalis decompofe it.

In the hiftory of this acid we have feen,
that when diftilled from the calx of man-
ganefe, it becomes white, and approaches
to the metallic ftate, by giving out a part of
its oxyginous principle to the muriatic acid;
or by taking away a portion of phlogifton,
which Mr. Scheele admits to exift in this
faline fubflance. The marine acid feems
to have a ftronger affinity with manganefe,
than the vitriolic ; for the folution of this
femi-metal by the latter, being poured into
fpirit of fait, forms a precipitate, which
Bergman found to be muriate of magnefia,
by the property it has of diflblving in fpi-
rits of wine ; a property which the vitriol
of the fame metal does not poffefs.

The fiuor acid diflblves the calx of man-
ganefe very fparingly, Thsfe two fubftan-
ces are more eafily united, according to
Scheele, by decomposing the vitriol, the
nitre, or the muriate of manganefe, by am-
moniacal fluor.

The cretaceous acid diflblves a fmall
quantity of manganefe, by digeftion in the
cold. The vegetable alkali, or fimple ex-
pofure to air, precipitate the metallic calx
from this acid.

Scheele has examined the adtion of nitre,
borax, and fal-ammoniac, on the calx of
manganefe. This calx difengages the acid

of

30 MANGANESJE.

of nitre, by theaffiftance of heat; with vege-
table alkali it forms a deep green mafs, folu-
ble in water, to which it communicates the
fame colour. The greennefs arifes from the
iron contained in the manganefe; and in
proportion as this falls down, the folution
becomes blue. Water and acids precipitate
this alkaline folution.

Nitre heated in veffels made of glafs,
containing calx of manganefe, communi-
cates a violet colour to the glafs, which is
fo much the deeper, as the calcination of
this calx by the nitrous acid, is more com-
plete.

Borax, melted with calx of manganefe,
aflumes a brown, or violet colour.

Sal-ammoniac diftilled from this metallic
calx, affords volatile alkali, in part decom-
pofed. Scheele, who made the fame obfer-
vation, informs us, that an elaftic fluid,
which he efteems to be one of the principles
of volatile alkali, is at the fame time difen-
gaged. But he has not pointed out the na-
ture of this fluid, which Mr. Berthollet has
difcovered in another way. This laft chemift
decompofes the volatile alkali, by means of
metallic calces ; in which procefs water is
formed by the union of inflammable gas,
one of the principles of this fait, with the
oxyginous principle of the calces, while the
atmofpheric mephitis, or the other princi-
ple of the volatile alkali, is difengaged in the
aeriform ftate.

The

MANGANESE. 31

The action of inflammable gas, of ful-
phur, or of plumbago, on manganefe, or on
its natural calx, is not known; arfenic, in
the calciform (late, appears capable of tak-
ing from this laft a portion of its oxyginous
principle, fince it deprives glafles of colour,
after they have become brown by means of
manganefe. Scheele believes that this phe-
nomenon is a confequencs of the manga-
nefe depriving the calx of arfenic, of the
phlogiiton it (till retains, and to which the
manganefe has a ftrong affinity.

The action of manganefe on neutral falts
is not known : it gives a violet colour to
borax and nitre, and caufes the fame colour
to appear in glafles which contain this me-
tallic calx.

To thefe properties Bergman adds, that
manganefe cannot be abfolutely purified from
the iron it already contains, and therefore,
this femi-metal, like nickel, has not yet
been obtained in a ftate of perfect purity.
Scheele, in the accurate analyfis which he
has made of the natural calx of manganefe,
found it to contain iron, lime, ponderous
earth, and a fmall proportion of quartz.

The black calx of manganefe, called black
magnefia, is ufed in glafs-houfes, to take
away the yellow, green, or blue tinge from
glafs, intended to be of a clear white; a large
proportion gives glafs a violet colour. Scheele
thinks that this mineral deprives glafs of its

colour,

32 ANTIMONY.

colour, by combining with the phlogifton
o£ inch matters as alter it ; but it is more
probable that this phenomenon is a confe-
quence of the action of the vital air fepa-
rated from mangahefe by heat, on the co-
louring fubftances. Manganefe is at pre-
fent uled in chemiftry, to prepare the aerat-
ed or oxyginous marine acid.

CHAP. XII.
Of the Regulus of Antimony.

THE regulus of antimony, flibium, which
ought to be called fimply, antimony, is
a heavy femi-metal, of a brilliant white, re-
fembling that of tin, or filver ; it is compo-
fed of plates applied upon each other, and
prefents on its furface a fort of cryftalliza-
tion, in the form of a flar, or leaves of fern.
It is likewife capable of cryftallizing in tri-
hedral pyramids. Immerfed in water, it
lofes t of its weight. It is eafily reduced
into powder, and has a very fenfible tafte,
or a&ion on the ftomach, being powerfully
emetic and purgative.

The regulus of antimony is feldom found
native. It has been difcovered by Mr. An-
thony Shwab, at Salberg in Sweden. Mr.
Schrieber, diredlor of the mines at Almont,
in Dauphiny, found it in thofe mines.

This

ANTIMONY. 33

This native antimony is in large plates, and
poffefles all the properties of that procured
by art, excepting that it contains one or
two hundreth parts of arfenic.

Mr. Mongez, the younger, has difcovered
a native calx of antimony, in fine white
needles, mixed with antimony, or grouped
fo as to refemble zeolite. He found this
calx on native antimony from Chalanges in
Dauphiny.

This femi-metal is mod commonly com-
bined with fulphur, and then forms what
is improperly called antimony, and ought
to be denominated ore of antimony. Thi*
mineral is of a blackifli grey, in brit-
tle plates or needles, of various magnitudes,
joined together in different forms. It is
fometimes mixed with other metals, parti-
culary lead and iron ; and is very com-
mon in Hungary, and in the provinces
of Bourbon, Auvergne, and Poitou. Natu-
ralifts have multiplied the varieties of an-
timony, accordingly as the fibres of the
mineral are parallel, divergent, irregular,
chatoyant, &c. When antimony is mixed
with a portion of arfenic, or when it is al-
tered by alkaline and hepatic vapours, its
needles are of a deep red, nearly reiemb-
ling the fine flowers of cobalt, but rather
more opake. The following are admitted
as varieties of this ore.
Vol, III. C Variety

34 ANTIMONY.

Variety

i . Antimony cryftallized in feparate hexa-
hedral priims, terminated by tetra-
hedral obtufe angled priims.

2. Striated antimony, in the form of large

irregularly formed needles, united in
fhapelefs maffes.

3. Antimony with divergent needles, iflu-

ing from one common center.

4. Lamellated antimony, the lamina? of

various fizes, and refembling the
lead ore called galena. This variety
is fometimes brilliant, and is then
called fpecular antimony.

5. Red antimony. It has the appearance

of a granulated efflorefcence, on the
furface of the needles of antimony ;
it is fometimes cryftallized in red
needles, or priims, of various de-
grees of brilliancy. Some natura-
lifts call this native kermes, or gold-
en fulphur of antimony.
The ores of antimony are not commonly
treated with the intention of feparating the
femi-metal. In general, nothing more is
done than the application of a fufficient
heat to feparate the fulphurated femi-metal
from its gangue, and other metallic matters
with which it may be mixed. For this
purpofe two earthen pots are taken, one of
which is pierced at the bottom in many
places 5 into this the ore is put; another

pot

ANTIMONY. 35

pot placed below the firfl, for the purpofc
of receiving the antimony in proportion as
it melts, being funk into the earth. A fire is
then made about the fuperior pot, fo as to
produce a mild heat at the beginning, becaufe
the antimony is very fufible; but towards
the end the heat is raifed, that the whole of
the antimony contained in the mineral may
be melted out. At this period of the pro-
cefs a portion of other metals falls down,
more efpecially iron, and forms a bed of
fcoriae on the furface of the antimony.
Though the antimony of Hungary is reck-
oned the pureft, it is certain that all anti-
mony which has been melted, if it be in the
form of perfect needles, and without mixture
of fcorias, is equally proper for all the ufes
in which this mineral is employed. It muft
only be obferved, that antimony often differs
in the relative quantity of fulphur and regu-
lus which it contains, and that it is of great
confequence to make an affay of fuch fpeci-
mens as are intended to be ufed in the pre-
paration of fuch antimonial medicines, as are
intended in all cafes to have the fame force
or efficacy.

The procefs employed to feparate anti-
mony from its gangue, fhews that it is
very fufible. If the fire be raifed when
it is melted in open veflels, it parts with
the fulphur, which is diffipated in yellow
flowers. The metallic partis likewife very

C 2 eafily

36 ANTIMONY.

eafily calcined, and diffipated in white
flowers. But if a mild heat, not fufficient
to melt the antimony, be employed, the ful-
phur of the mineral is diffipated flowly,
and by degrees ; the metal uniting gradual-
ly to the bafe of vital air, and forming the
grey calx of antimony. This operation
cannot be well performed, unlefs the an-
timony be in a ftate of minute divifion, fo
as to prefent a large furface to the air. It
is therefore reduced to powder, and expo-
fed to a low heat in a mallow veflfel of
glazed earth. The procefs muft likewife be
conducted with caution at the beginning,
becaufe of the fufibility of the antimony;
but in proportion as it goes on, and the
fulphur is diffipated, the antimony becomes
more refractory, and the fire. may be raifed
to fuch a degree as to make the capfule, in
which the mineral is contained, red hot.
It is a proof that the operation is well con-
ducted, when no other fmell but that of ful-
phur is perceived during the roafting, and
the matter does not gather into clots. But
when, on the contrary, the antimony gathers
together in lumps, and the fulphur is de-
compofed during • its volatization, which
may be perceived by the fuffocating fmell
of volatile fulphureous fpirit, the heat is too
great, and muft be diminifhed.

Though fulphur feems to adhere very
weakly to the regulus of antimony, in the

ore

ANTIMONY. 37

ore wc are treating of, it is not poffible to
drive it off intirely by roafting -, and the
grey calx of antimony always retains a corr-
fiderable quantity, notwithstanding the cal-
cination has been carried on to fuch a de-
gree, as to deprive the metal of its reguline
properties.

The grey calx of antimony urged by heat,
without addition, melts into a glafs of a red
brown, or hyacinthine colour. This glafs is
varioufly fufible, and has different degrees of
tranfparency, accordingly as the metal made
ufe of was more completely calcined. If the
calx contain a fmall proportion of fulphur,
and a larger of the oxyginous principle, the
glafs it affords is transparent, and lefs fufi-
ble ; and is glafs of antimony properly fo
called. But if the calx contain much fulphur,
and ftill nearly approaches the metallic itate,
it produces a more fulible and more opake
glafs; this is called liver of antimony, be-
caufe of its dull red colour, refembling the
liver of animals. When the calx of anti-
mony has been calcined fo perfectly, as that
it is difficult to bring it into fufion, a fmall
piece of fulphur, or of crude antimony, may
be thrown into the crucible, and the matter
inftantly melts.

The grey calx of antimony, the liver, or
the glafs, being heated in a crucible with
their own weight of black flux, and a fmall
quantity of black foap, or oil, are reduced,

C 3 and

38 ANTIMONY.

and afford the pure regulus of antimony.
The black flux in this operation, anfwers
two intentions ; the alkali which it contains
unites to the fulphur, which has not been
diffipated from the ore by the action of the
fire, and the coaly matter favours the re-
duction of the metallic calx. This is the
method of preparing the regulus of anti-
mony in the large way for commercial pur-
pofes. The regulus is caft into flat globu-
lar pieces, which have a cryftallization on
their furface, in the form of the leaves of
fern.

The regulus of antimony is fcarcely al-
tered by the contact of light. It does not
melt till after ignition, and if it be flrongly
heated in clofed veflels, it is intirely volati-
lized without decompofition. If it be fuf-
fered to cool flowly when melted, and the
fluid portion be poured out after its furface
is become congealed, the remaining part is
found to be cryftallized in pyramids, or
quadrilateral pieces, as we have already
obferved.

The regulus of antimony melted in open
veflels, is quickly calcined. White thick
fumes arife, which fall again on the furface
of the melted metal, or adhere to the cover
of the crucible, in the form of fmall needles.
This is a perfect metallic calx, to which the
names of argentine, or filvery flowers of re-
gulus of antimony, or fnow of antimony,

have

ANTIMONY, 39

have been given. To prepare fmall quanti-
ties, a crucible is placed horizontally in a
furnace, fo that its rim applies to the opening
of the furnace to which it is luted with clay,
Regulus of antimony is put into the cruci-
ble, and the fire railed furficiently to melt it,
and caufe it to emit fumes. The fmoke
being received in a fecond crucible applied
to the firft, becomes condenfed in very {len-
der white and brilliant needles, which ap-
pear to be quadrangular prifms. The fnow
and the flowers of antimony are not only
fufceptible of volatization at the time of the
deflagration, or burning ofthefemi-metal, but
fublime alone if again urged by a ftrong heat.
This calx may likewife be melted into an
orange-coloured glafs, paler and more tran-
fparent than is made with the grey calx of
antimony. It is likewife much lefs fufible.
The regulus of antimony is not altered by
the adlion of combuftible matters, but the
fnow of antimony is decompofed by fub-
ftances of this nature, and refumes the
reguline ftate. As this calx is highly cal-
cined, and charged with a large proportion
of the oxyginous principle, it very diffi-
cultly aflumes the metallic ftate; and as it
is likewife very volatile, it cannot be
reduced but in clofe veflels. It even
appears to be foluble in water, and to pof-
fefs certain faline characters. Rouelle is
the firft who made this obfervation ; and as
C 4 feveral

4*0 ANTIMONY.

feveral other metallic calces, and in particu-
lar that of arfenic, become faline and acid
when they are faturated with the oxyginous
principle, it may probably be hereafter dis-
covered that the flowers of antimony pof-
fefs the fame property.

The regulus of antimony is fcarcely at all
changed by expofure to air, it being only
obferved that its furface becomes tarnifhed.
It is not foluble in water, though feveral
phyficians have fufpected that it commu-
nicates an evident emetic quality to that
fluid. The fnow and the flowers of antimony
diffblved in water, communicate an eme-
tic property ; this action of the calx of anti-
mony, together with its folubility in water,
and its volatility, {hews, as we have ju ft ob-
ferved, a fort of analogy between it and the
calx of arfenic. Many mineralogifts have
hence fuppofed, that the ore of antimony is
never free from arfenic ; and it is certain,
that this ore in powder, thrown on hot
coals, as well as the regulus, emits an odour
fenfibly arfenical; and that when the ope-
rator has been expofed during a certain time
to this vapour, he experiences its cathartic
effects, and other fymptoms of being (light-
ly poifoned, as I have myfelf feveral times
obferved in my laboratory.

Earthy fubftances have no action on the
regulus of antimony. Its calx enters with-
out difficulty into the compofition of glafles,

and

ANTIMONY. 41

and gives them an orange colour, refem-
bling that of the hyacinth.

The adtion of the falino-terreftrial fub-
ftances, and alkalies, on the regulus of anti-
mony, is not known ; but the adlion of
acids on this femi-metal has been more at-
tended to.

When oil of vitriol is flowlv boiled on the
regulus, the former is decompofed and the
latter partly calcined ; a large portion of ful-
phureous gas is exhaled, and towards the end
a fmall quantity of fulphur fublimes. The
mafs remaining after the decompofition of the
acid, confifts of much metallic calx, and a
fmall proportion of femi-metal, combined
with the acid in the ftate of vitriol of the
regulus. The faline part may be feparated
by means of diftilled water. This fait, when
brought to a dry ftate by evaporation, is very
deliquefcent, and cannot be made to afford
cryftals. Fire eafily decompofes it; pure
water, the falino-terreftrial fubftances, and
alkalies, likewife feparate thefe principles.
The calx formed by the folution, and preci-
pitation from the vitriolic acid, is very dif-
ficult of redudlion.

The nitrous acid brifkly attacks the regu-
lus of antimony, calcining a great part, and
diftblving the reft, the acid being at the
fame time quickly decompofed. This fo-
lution may be well made in the cold. The
fait which is produced, being feparated from

the

42 ANTIMONY.

the calcined part by lixiviation, affords an
antimonial nitre, which is very deliquefcent,
decompofable by fire, and by the fame inter-
mediums as the vitriol of the regulus. The
calx of antimony, formed by the nitrous
acid, is very white, and is at the fame time
exceedingly refractory, and difficult of re-
duction.

The muriatic acid appears to act with
more difficulty on the regulus of antimony,
than the other acids ; it however diflblves
it by the help of a long digeftion, and cal-
cines it lefs than either the vitriolic, or ni-
trous acid. I have obferved, that when this
acid is left for a long time on the regulus in
powder, it acts flowly, and diflblves a con-
iiderable quantity. The antimonial muri-
ate, which is obtained in fmall needles, by
a flrong evaporation, is very deliquefcent,
melts in the fire, is volatilized, and is de-
compofed by diftilled water, like the butter
of antimony, from which it does not feem
greatly to differ. Mr. Monnet, who has
well defcribed this combination, as effected
by a confiderable heat, obferves, that the
combination made with a calx of antimony,
(as for example, the argentine flowers) differs
greatly from that which is prepared with
the regulus, in its fixity and manner of cry-
ftallizing in laminae, like felenite and feda-
tive fait. This fait is befides decompofable
by water. We have had occafion to obferve,

that

ANTIMONY. 43

that in the folutions of the regulus by the
muriatic acid, or by means of diftillation,
there is always a faline portion which does
not rife by the a&ion of fire, and refembles
that which Mr. Monnet makes mention of.
This depends on its having been ftrongly
calcined by the acid. The fame obfervation
applies equally to almoft all metallic folu-
tions which exift in different ftates, accord-
ingly as they contain metals more or lefs cal-
cined. Mr. Monnet has eftablifhed the facfr,
that twelve grains of calx of antimony are
fufficient to faturate half an ounce of com-
mon muriatic acid, of which however he
has not determined the ftrength. Bergman
affirms, that the muriatic acid has a ftrong-
er affinity with antimony than the other
acids have.

Aqua regia difiblves the regulus of anti-
mony more readily than either of the acids
which compofe it ; becaufe the force of the
nitrous acid is fufficiently moderated, to
prevent the regulus from being intirely cal-
cined ; and, on the other hand, the activity
of the muriatic acid is increafed, on account
of its union with the oxyginous principle,
feparated from the nitrous acid. The fait
formed by the folution of the regulus in
aqua regia, is very deliquefcent, and may be
decompofed like the other faline combina-
tions of this femi-metal.

Antimony,

44 ANTIMONY.

Antimony, or the natural combination of
fulphur with the regulus, is in general more
jbluble, and is lefs calcined by acids than
the femi- metal itfe f. It feems as if the
fulphur partly defended the regulus from the
aftion of thefe faline fubftances. Aqua re-
gia has a moderate acftion on this mineral.
It is a very good menftruum for feparating
the fulphur, which precipitates under the
form of a white powder. Mr. Baume di-
rects that aqua regia, compofed of four
parts of nitrous, and one of marine acid,
fhould be employed in this operation.
When the adlion of the acid is over, the folu-
tion may be filtered, and the fulphur remains
en the filtre. The weight of this fhews the
refpe&ive quantities of fulphur and regulus
contained in the antimony. It mufl how-
ever be obferved, that the fulphur, thus fe-
parated, is always mixed with a fmall quan-
tity of the calx of antimony ; fo that this
experiment cannot be efteemed as very exafr,
unlefs the portion of calx, mixed with the
fulphur, be previoufly feparated by means
of acids.

The effeft of other acids on the regu-
lus of antimony, has not yet been exa-
mined.

This femi-metal decompofes many natu-
ral falts. Mr. Monnet, in his treatife on
the folution of metals, has defcribed an ope-
ration, by which he fhews, that the regu-
lus

ANTIMONY. 45

lus decompofes vitriolated tartar. He melt-
ed in a crucible a mixture of one ounce of
this fait, and half an ounce of the femi-
metal. A yellow, vitriform, exceedingly
cauftic mafs was produced, which was found
to be an antimoniated liver of fulphur.
This mafs, being wafhed with hot water,
afforded, by cooling, a reddifh fulphur of
antimony, or true kermes. He is of opi-
nion, that the phlogifton of the regulus is
united to the vitriolic acid with which it
forms fulphur, and that the alkali of the vi-
triolated tartar, compounded with this ful-
phur, produces a liver of fulphur, which
difTolves the calx of antimony. It will
eafily be underftood, that according to the
new do&rine, the femi-metal feizes the oxy-
ginous principle of the acid, which laft, by
that means, is converted into fulphur. A
feries of experiments, which I have made on
this fubjedt, have convinced me, that many
metallic fubftances are capable of decom-
pofing vitriolic falts, in the fame manner,
as I fhall fhew in the following chapters.

Nitre is decompofed very readily by the
regulus of antimony. When equal parts of
this femi-metal and of nitre in powder are
thrown by fmall portions at a time into a
red hot crucible, a ftrong detonation takes
place, and the regulus is burned by the
afliftance of the vital air afforded by the
nitre. After this operation, the crucible

is

46 ANTIMONY.

is found to contain the fixed alkali or bafe
of the nitre, and the antimony in the ftate
of a white calx. This calx is called dia-
phoretic antimony. The regulus of anti-
mony is not ufually employed in this ope-
ration, but the mineral or antimony itfelf :
in which cafe, a larger quantity of nitre is
required to be added; as for example, three
parts to one of the mineral, in order
that not only the regulus may be burned,
but likewife all the fulphur to which it is
united. The reafon why the mineral is
preferred in this procefs is, that the fulphur
of the antimony renders the detonation of
the nitre more rapid, and Angularly facili-
tates the combuftion of the regulus.

The matter that remains in the cruci-
ble after the detonation, is compofed of the
calx of antimony, united partly to the fixed
alkali of the nitre, and partly to a portion
of the nitre, which efcaped the detonation.
It likewife contains a fmall quantity of vi-
triolated tartar formed by the acid of the
fulphur, and the fixed alkali of the nitre.
This compound is called the folvent of Ro-
trou, or unwarned diaphoretic antimony.
The matter being thrown into hot water,
the faline part is diflblved, and the metallic
calx remains fufpended. The water is
poured off before fubfidence, and the white
and fixed calx is then fuffered to fall down ;
this is called wafhed diaphoretic antimony.

It

ANTIMONY. 47

It muft be carefully dried, and then mould-
ed into little fquare pieces. The water,
which floats above, holds in folution the
faline matters which were contained in the
mixture, and alfo a portion of the metallic
calx united to the alkali of nitre. If an
acid be poured on this liquor, it feizes the
alkali, and the antimonial calx is precipi-
tated. This calx is called cerufe of anti-
mony, or the materia perlata of Kerkringius.
The liquor, which remains after the precipi-
tation of theperlate matter, contains a fmall
quantity of nitre, a fmall quantity of vitrio-
lated tartar, and the new neutral fait, form-
ed by the union of the acid to the alkali,
which holds the metallic calx in folution.
Though the laft fait varies according to the
acid made ufe of, it is very improperly cal-
led antimoniated nitre of Stahl. This fait
in general is not nitre, becaufe the vitriolic,
or muriatic acids are ufually applied to pre-
cipitate the calx of antimony -, and when the
precipitation is well made, no part of the
calx remains in the fait.

The diaphoretic antimony and the cerufe
may be melted into glafs, as well as all the
other calces of this femi-metal ; but as they
are in a very perfect ftate of calcination,
they cannot be fufed without confiderable
difficulty. For the fame reafon they are
not eafily reduced into the reguline form.
They feem to be more difficult of reduction

than

48 ANTIMONY.

than even the fnow of antimony, though they
have ftronger medical properties. They are
likewife lefs foluble in water and in the
acids.

The regulus of antimony appears capable
of decompofing marine fait ; for if a mix-
ture of thefe two fubftances be heated in a
retort, butter of antimony pafles over into
the receiver, according to the obfervation of
Mr. Monnet. This chemift has not defcrib-
ed the refidue of the operation.

Regulus of antimony does not readily de-
compofe fal-ammoniac, according to Buc-
quet, and butter of antimony is not obtained
in this procefs, as Juncker affirms.

All combuftible matters a<ft more or lefs
on this femi-metal. Inflammable gas alters
its furface, and gives it a darker colour.
It acfts in a much more efficacious manner
on its folutions. I have caufed this gas,
obtained from iron by fpirit of vitriol, to
pafs through a folution of antimony in aqua
regia. The latter immediately became
turbid, and depofited a yellow orange
coloured matter, fimilar to the golden ful-
phur, but never refembling kermes. The
flowers of antimony, and diaphoretic anti-
mony, whether dry, or moiftened with
water, being expofed in the fame manner to
the aqueous inflammable gas, did not appear
to be at all changed.

Sulphur

ANTIMONV. 49

Sulphur combines very readily with the
regulus, and forms an artificial ore, per-
fectly fimilar to natural antimony. To ob-
tain this combination, equal parts of fulphur
and of the regulus are to be quickly melt-
ed in a crucible. A mineral in the form of
needles of a deep grey is produced, which
never contains fo much as the half of its
weight of fulphur, unlefs one part and a half
of the latter fubftance be ufed with one part
only of the femi-metal. I have likewife ob-
ferved, that one ounce of the regulus melt-
ed in a retort, with one ounce of fulphur,
produced ten drachms of antimony, which
confequently did not contain more than
two drachms of fulphur ; and that the reft
of this combuftible matter, fwelling up by
the fufion, patted into the receiver. No
more than one part of fulphur therefore is
required to give the characters of antimony
to four parts of the regulus ; and hence we
may obferve, how neceffary it is to make an
affay of antimony before it is ufed for me-
dical purpofes, in order that the effect of
different fubftances combined with this me-
tal may be properly eftimated.

Liver of fulphur completely diffolves re-
gulus of antimony, and forms a yellowifh
mafs, from which antimoniated fulphur may
be precipitated by any acid. Hepatic gas
acts on the folutions of this femi-metal, ab-
folutely in the fame manner as the inflam-

Vol, III, D mable

^u%

ANTIMONY.

toabl^j^s obtained by means of diluted
yi$r$£#c acid ; which inflammable gas is
^tfduced by the decompofition of water,
as we fhall ihew in our hiftory of iron.

Regulus of antimony unites with arfenic
and with bifmuth, but thefe alloys have not
yet been carefully examined.

Such are the principal properties of this
femi-metal. It is likewife neceflary to con-
fider its ore, which is improperly called an-
timony. As this mineral is ufed in the
preparation of a great number of import-
ant remedies, it follows of courfe, that its
properties are much better known than thofe
of the femi-metal it contains. The labours
of the alchemifts with this mineral have
multiplied our knowledge concerning it,
and no fubftance has afforded materials for
a greater number of experiments. We have
already feen, that by means of heat, a por-
tion of the fulphur may be feparated -> that
a grey calx refults from this operation,
which may be melted into glafs, or liver of
antimony, accordingly as its calcination has
been more or lefs perfectly performed.
That nitre, at the fame time that it burns
the fulphur, likewife calcines this metallic
matter. But roafting, and combuftion by the
addition of nitre, are not the only means of
feparating the fulphur of antimony. This
may be done by prefenting to the mineral
a body, which has a ftronger affinity with

cither

ANTIMONY. 51

either of its component parts, than that part
has to the other.

We have an inftance of this kind of
decompoiition, in applying acids to crude
antimony. Thefe fairs, and efpecially aqua
regia, diilblve the femi-metal, and fepa-
rate the fulphur which then floats above.
The regulus appears to be more eafily
and completely diftblved when in anti-
mony, than when it is pure, as has been
before remarked. Iron, and other metallic
fubftances, deprive the regulus of its ful-
phur.

Nitre is employed with fuccefs in the
preparation of many valuable antimonkl me-
dicines. We have already feen, that when
one part of antimony is detonated with
three parts of nitre, the fulphur and the
regulus are burned, and the relidue is a
white metallic calx mixed with alkali. If
equal parts of nitre and antimony be de-
tonated together, the detonation is of courfe
weaker. For this reafon it is neceflary
to throw the mixture by fpoonsful into a
red hot crucible ; whereas the other pro-
portion ufed in the making of diaphoretic
antimony, need only be once fet on fire,
when it continues to detonate, till it is intire-
ly reduced to a white mafs. When the deto-
nation of the antimony and nitre, mixed in
equal parts, is finifhed, the fire is increafed, fo

D 2 as

52 ANTIMONY.

as to melt the whole ; and inftead of a dia-
phoretic antimony, a brown opake brilliant
brittle mafs is found in trie crucible, which
is a true liver of antimony covered with
fcoriae. In this operation the nitre is not
fufficient in quantity to burn all the fulphur;
the remainder therefore holds the calx of an-
timony in folution. When the mixture is
not heated fufficiently to melt it, nothing
is obtained but a nitrous fcoria, to which
the name of falfe liver of antimony of Rut-
land is given. This matter reduced into
powder, and wafhed with water, forms
crocus metallorum ; which is merely liver
of antimony pulverized, and feparated from
the faline matters produced by the detona-
tion of the nitre.

There are two other preparations ana-
lagous to the foregoing, which are true
livers of antimony ; the one is the ruby of
antimony, or magnefia opalina, made by
melting together equal parts of decrepitat-
ed marine fait, nitre, and antimony. This
fufion, which takes place without detona-
tion, affords a vitreous mafs of a brown
colour, very brilliant, and covered with
white fcoriae. The other, improperly called
the medicinal regulus, is prepared by fufing
a mixture of fifteen ounces of antimony,
twelve ounces of decrepitated marine fait,
and three ounces of tartar. The refult is
a black fliining very opake denfe glafs, not

at

ANTIMONY, 53

at all metallic in its appearance. Thefe
two compounds, which differ from the true
liver of antimony in certain extraneous pro-
perties, doubtlefs owe this difference to the
marine fait which enters into their prepara-
tion, and whofe effedt on the mineral has
not yet been afcertained.

When the regulus of antimony is required
to be prepared in the fmall way in labora-
tories, no more nitre (hould be made ufe
of than is neceflary to burn the fulphur,
and a fubftance capable of affifting in the
reduftion of the regulus muff be added.
With this intention, eight ounces of anti-
mony in powder, fix ounces of tartar, and
three of nitre, are taken. Thefe are mixed
very accurately, and thrown by fpoonsful
into a red hot crucible. The nitre deto-
nates with the tartar and the antimony ;
black flux is formed, and the regulus of
antimony melts and flows to the bottom.
When the matter is well mfclted, it is to
be poured into an iron cone, greafed and
made hot. The cone muff be ftruck feve-
feveral times during the pouring of the
mixture ; after which, the whole being
fuffered to cool, the regulus of antimony
is found at the bottom. The femi-metal
is covered with black and reddifh fcorias,
which rapidly attract the humidity of the
air. When the regulus is pure, its upper
furface is convex, and prefents the regular

D 3 figure

54 ANTIMONY.

figure of a ftar, which the exalted imagi-
nation of the alchemifts led them to attri-
bute to various caufes. But it depends Am-
ply on the manner of the cryftallization of
the regulus during its cooling. The cool-
ing begins at the fides, and the fluid mat-
ter being prefied out from the center to-
wards the circumference, produces this ap-
pearance, which takes place only when the
mafs of regulus is fmall ; for in the large
maffes of this femi-metal, the undulation
of the fluid matter refpefts feveral centers,
and inftead of a ftar, it is found marked
with impreflions in the form of leaves of
fern, which cryftallizes under different an-
gles. Reaumur has fliewn, that a fudden
cooling prevents this kind of cryftallization
in the form of a ftar ; and that if one fide
of the cone be quickly cooled, no more
than half a ftar will be feen *. The quan-
tity of regulus obtained by this procefs,
does not amount to the half of the anti-
mony made ufe of, though this mineral
often contains more regulus of antimony
than fulphur. This is caufed by a portion

* There is doubtlefs a relation between the manner in
which metallic buttons cryftallize at their furface, and the
form which they affecl, when by careful cooling, and a
feparation of the fluid portion, they are difpofed in fingle cry-
flals. The Abbe Mongez is bufied in inquiring into this re-
lation in his refearches on tbe cryftallization of metals. F.

of

ANTIMONY. $$

of the femi-metal combining with the fa-
line matters which form the fcoria?.

The fcoria?, which flow above the regu-
lus of antimony extracted by this procefs,
are of a very compound nature. They con-
tain the fixed alkali of the nitre, and of
the tartar united to the fulphur of the an-
timony, and in the ftate of an hepar. This
hepar holds a portion of the calx in folu-
tion, and is befides mixed with a fmall
quantity of vitriolated tartar, formed by the
vitriolic acid produced in the cornbuftion
of the fulphur, and united to a portion of
the vegetable fixed alkali. 'Befides which,
they contain a coaly matter afforded by the
tartar. If thefe fcorice be boiled in a large
quantity of water, and the hot liquor be
filtered, the coaly portion remains on the
filtre, and the liquid, which is clear while
it continues hot, becomes troubled by cool-
ing, and depofits a reddifh matter, which
has been hitherto considered as an antimo-
niated liver of fulphur. The precipitate
is called kermes mineral by the dry way.
When the liquid affords no more, it may
be evaporated, and a matter lefs coloured
than the kermes is obtained, or true anti-
moniated liver of fulphur. It likewife af-
fords vitriolated tartar. If inftead of eva-
porating the liquid, any acid be poured in,
a yellow orange precipitate, called the gold-
en fulphur of antimony, is produced, which

D \ does

56 ANTIMONY.

does not appear to differ much from the
kermes.

If antimony broken into fmall pieces be
boiled, for a Ihort time, in water charged
with mild vegetable or mineral alkali, the
alkali diffolves the fulphur of the antimony,
and forms a hepar, which holds a part of
the calx of antimony in folution. This
boiling liquor being filtered, and fuffered
to cool, the kermes which it contains pre-
cipitates ; and the cold liquor being filtered,
the golden fulphur may be precipitated by
means of acids. If an alkaline lixivium
be boiled again on the refidue of the anti-
mony, more kermes may be obtained, but
this kermes is paler than the foregoing ;
and the oftener the operation is repeated,
the lefs kermes is afforded by the antimony.
The alkali appears to diffolve more ful-
phur than regulus, and the mineral fhould
not be boiled more than once or twice.
This operation is called in general the pre-
paration of kermes by the humid way.

The name of kermes was given to this
preparation by a Chartreux friar named
Simon, doubtlefs on account of its colour,
which refembles that of the animal called
kermes *, which is employed in dying.
Kermes mineral has likewife been called

* The animal kermes, or fcarlet grain ufed in dying, is
the (kin of a female infect, which fixes on the holm or
ilex, and becomes extended by degrees in the manner of

a fmall

ANTIMONY. 57

Poudre des Chartreux, becaufe it was firft
prepared by perfons of that religious order.
The difcovery of this medicine is due to
Glauber, who prepared it with antimony,
and a folution of nitre fixed by coal ; but he
has defcribed his procefs in an unintelligible
manner, and almoft intirely under alche-
miftical emblems. Lemery, who laboured
much with antimony, and who has given
us a preparation analogous to kermes, under
another name, may be regarded as the true
inventor. This remedy, however, was of-
fered to the public as an intirely new in-
vention many years after the publication of
the works of that chemift, and in facft owes
its celebrity to the lingular cures effected
by means of it in the hands of brother Si-
mon. This friar had the compofition from
a furgeon named La Ligerie, who was not
himfelf the inventor. This laft affirmed that
he received it from Mr. Chaftenay, lieute-
nant in the army at Landau, to whom it
had been communicated by an apothecary,
who pretended to be a difciple of Glauber.
Mr. Dodart, then firit phyfician to the king,

a fma!l cap or button ; it has loft the form of rings, by
which thefe animals are known : it is beneath this cap,
that the eggs it contains are inclofed. The infects pierce
the fhell, and ifTue out, and the females, not having wings,
fix and die on the leaves of the tree, after having been
fecundated by the males, who have wings. Cochineal is
another fpecies of infect: fimilar to this, as we fhall fnew
in our account of the animal kingdom. Fourcrov.

lied

58 ANTIMONY.

applied to La Ligerie to publifh the receipt
of kermes, which he accordingly did in the
year 1720. ' Lemery the younger claimed
the difcovery in the name of his father in
the Memoirs of the Academy, and with
great juftice, as moil chemifts ftill make
ufe of the procefs invented by him for the
preparation of this remedy.

The procefs defcribed by La Ligerie con-
fifts in boiling for two hours a pint of rain
.water, with four ounces of the liquor of
nitre fixed by charcoal, and a pound of anti-
mony broken into fmall pieces. The boil-
ing liquor is filtered, and the fame anti-
mony is again boiled with three ounces of
frefh lixivium, diluted in a pint of rain
water. Laflly, The fecond refidue is boiled
a third time with the preceding lixivium ;
two ounces of liquor of fixed nitre, and a
pint of rain water being added. It is then
filtered, and the kermes fuffered to fettle,
which being warned till it is infipid, is then
dried ; and laflly, after fpirit of wine has
been burned upon it, it is reduced to pow-
der. This procefs is very long, and affords
but a fmall quantity of kermes ; not more
than two or three drachms from a pound of
antimony. It is moreover very trouble-
fome on account of the long ebullition, and
the evaporation of the water. Laflly, It
occafions a lofs of more than three quarters
of the antimony, on account of the fmall

quantity

ANTIMONY. 59

quantity of alkali employed in proportion
to that of the mineral.

Mr. Baume, who adopted the procefs
of Lemery, gives two methods for the eafy
preparation of a large quantity of kermes
in a fhort time ; the one by the dry, and
the other by the humid way. According
to the firfi: method, one pound of antimony
is melted in a crucible, together with
two pounds of very pure fait of tartar, and
one ounce of fulphur -, the whole being pre-
vioufly well pulverized. This melted mix-
ture is poured out into an iron mortar, is pul-
verized grofsly when cold, and is then boil-
ed in a fufficient quantity of water. The
liquor being filtered through paper, affords
a kermes of a red brown in cooling; whicn,
being firft wafhed with cold, and afterwards
with boiling water, till it is deprived of all
faline matter, is dried, pulverized, and paf-
fed through a fine fieve.

To prepare the kermes by the humid way
according to the fame chemift, a lixivium
of five or .fix pounds of cauftic fixed alkali
is boiled, with fifteen or twenty pounds of \
river water. Four or five ounces of anti-
mony previoufly levigated, is thrown into
this boiling liquor, and the mixture being
well agitated, and fuffered to boil for a
very fhort time, is poured on the filtre.
This liquor depofits much kermes during
its cooling, which is to be waflied in the

fame

60 ANTIMONY.

fame manner as the kermes produced by
fuiion. According to Baume, this laft pro-
cefs affords twelve or thirteen ounces from
a pound of antimony, and he affures us
that the two kermes are perfe<ftly fimilar.

The theory of this operation, and the
nature of kermes, are not yet perfectly
known, notwithstanding the labours of many
celebrated chemifts. It is generally thought
that the alkali diffolves the fulphur of the
antimony, and that the hepar it forms dif-
folves the regulus. The femi-metal, how-
ever, is not totally diffolved, fince in the
procefs of Lemery by the humid way, a grey
powder is precipitated during the ebullition,
which may be melted without addition into
a true regulus. The precipitation of the
kermes by the cooling of the lixivium,
which is at firft reddifli and tranfparent,
but lofes its colour in proportion as the
kermes is depofited, is a phenomenon ftill
more Angular. This compound is by others
thought to be a kind of antimony, with
an over dofe of fulphur, and foluble in the
hot alkaline lixivium. In fad:, if the alka-
line lixivium be heated on a certain quan-
tity of kermes ready prepared, a complete
folution will take place. The lixivium,
which has depofited kermes by cooling,
flill contains antimoniated liver of fulphur :
by the addition of any acid, an orange co-
loured matter is thrown down, called golden

fulphur

ANTIMONY, 6t

fulphur of antimony, which is much more
emetic than the kermes, and is fuppofed
to contain a lefs proportion of fulphur.

Geoffroy, who communicated in the years
1734 and 1735, feveral memoirs concerning
the kermes mineral, made a great number of
experiments with the intention of analyzing
it. The action of acids is efleemed the moft
efficacious means that can be employed for
that purpofe. It is thought that theie falts
diffolve the femi-metal, and leave the ful-
phur difengaged, and that the refpeftive
quantities of thefe two fubflances can be
thence eftimated. One drachm of kermes,
according to Geoffroy, contains fixteen or
feventeen grains of the regulus, thirteen op
fourteen grains of fixed alkali, and forty or
forty-one grains of fulphur. Many che-
mifts at prefent think, that the kermes does
not contain an atom of alkali. Mr. Baume
affirms, that this fait is not one of its con-
flituent principles, and that it may be in-
tirely deprived of it by fimple wafhing in
a large quantity of boiling water. Mr.
Deyeux, who has likewife made experi-
ments on this fubflance, is of the fame
opinion. I have had occafion to make th'e
fame obfervation in a feries of experiments
made in conjunction with the Duke de la
Rochefoucauld. But the moft important
circumftance relative to the kermes is, that
it appears to be a very different fubftance,

according

62 ANTIMONY.

according to the feveral circumftances at-
tending its preparation. It contains ful-
phur and regulus in various proportions ;
and there is reafon to apprehend, that its
effefts muft vary exceedingly, according as
the proportion of thefe fubftances differ.
In general, it feems that the ftate of the anti-
mony ; the variety of the proportions of its
component parts ; its greater or lefs divi-
fion ; the more or lefs cauftic ftate of the
alkali and its quantity ; the quantity of the
water j the time of ebullition ; and many
other analogous circumftances, occafion An-
gular variations in the nature of kermes.
In order that it may be the fame in all cafes,
it ought to be prepared with fubftances
always of the fame quality, and in circum-
ftances perfectly fimilar. Without entering
into any very long details concerning the
phenomena the kermes has prefented, when
treated by a great number of intermedia,
I fhall only add, Firft, that cauftic alkalis
greatly alter it, and diffolve it even in the
cold. Secondly, That acids a£t with very
different degrees of force on this fubftance*
and that it is exceedingly difficult to deter-
mine with accuracy, by means of acids, the
quantity, and the ftate of the femi-metal,
or of the fulphur, which enter into its
compofition, becaufe the fulphur, which is
feparated, always retains a certain quantity
of the calx.

Cauftic

ANTIMONY. 6$

Cauftic alkalies act much more ftrongly
on antimony than mild alkalies, and pro-
duce a much greater quantity of kermes of
a deeper colour. Lime, or lime-water, di-
gefted on antimony in powder, affords, even
without heat, in a certain number of days,
a kind of kermes, or golden fulphur, of a
beautiful red colour. Volatile alkali alters
it in the fame manner. When fal ammo-
niac is diftilled from antimony, a pulveru-
lent fublimate of a purple colour is ob-
tained, which appears to be a kind of anti-
moniated liver of fulphur, with bafe of
volatile alkali.

To conclude the hiftory of the decom-
pofition of antimony, we (hall add, that
many metallic fubftances have the property
of depriving it of its fulphur, by their
ftronger affinity to that fubftance. Tin,
iron, copper, and filver, produce thefe de-
compofitions. Tin or filver, being melted
together with antimony, unite with the
fulphur, and leave the regulus. Iron and
copper produce the fame effect, provided
they be firft reduced to filings, or very fmall
parts, and be previoufly made red hot before
the antimony is added. The mineral acce-
lerates the fufion of thefe metals, and the
regulus is feparated, The femi-metal ob-
tained by thefe proceffes, is not pure, but
retains a portion of the metallic fubftance
made ufe of to feparate the fulphur. Its

colour

64 ANTIMONY.

colour and appearance always indicate its
impurity ; it is diftinguifhed under the
names of jovial, cupreous, or martial regulus,
according to the metals to which it is united.

The regulus of antimony is employed in
many arts, and efpecially by the letter-
founders. It was formerly ufed as a purge.
Wine or water was poured into veffels made
of this regulus, and fuffered to ftand for
the fpace of a night ; and the following
day the liquor was drank : but as variations
of the temperature of the place in which
this operation was made, and of the acidity
of the wine made ufe of, muft have necef-
farily produced differences in the quantity
of regulus taken up, it is with juftice that
this medicine was abandoned, as not being
to be depended on. For fimilar reafons the
perpetual pills, or fmall balls of this regu-
lus, which were fwallowed as purges, have
been renounced. The ftate of the digeftive
juices, the nature of the mucus in the firft
paffages, and the fenfibility of different
individuals, muft have rendered their effefts
uncertain, and often dangerous.

Crude antimony, Rotrou's folvent, dia-
phoretic antimony, kermes mineral, and the
golden fulphur, are the only antimonial
medicines at prefent ufed.* Crude antimony
is employed as a fudorific in cutaneous dis-
orders. It is fufpended in a linen bag in

* Many other antimonial preparations are in common
ufe in Britain, for which fee the Diipenfatory. T.

the

ANTIMONY. 65

the veffels in which the ptifans appropriated
to thefe diforders are prepared -, but many
phyficians deny it to have any virtue when
adminiftered in this manner. It is like-
wife taken in fubftance, being firft finely
levigated, and made up into pills for the
fame purpofe.

The folvent of Routrou is greatly recom-
mended in lymphatic diforders, produced
the congelation of that liquid, as in fcro-
phulous affections, and in general in all glan-
dular tumours. Many phyficians have no
confidence in the effects of wafhed diapho-
retic antimony. They confider this medi-
cine as a pure calx of antimony, without
any virtue whatfoever. We cannot, how-
ever, forbear obferving, that this calx, in
which Rouelle the younger has obferved
a remarkable degree of folubility, may pro-
duce lingular effects in confequence of this
property. It is likewife certain, that as the
action of the gaftric and inteftinal juices on
metallic calces are not known, it cannot
therefore be determined whether a fubftance
infoluble and infipid to all appearance
has any virtue or no. Obfervation, how-
ever, teaches us, that this medicine pro-
duces but flight effects in eruptions, and
in the moft obftinate diforders of the ilun,
though employed for a long time. The
unwafhed diaphoretic antimony, or folvent
of Routrou, which is much more active

Vql, III. E than

66 ANTIMONY.

than the before-mentioned preparation, by
reafon of the alkali it contains, deferve to
be preferred. In thefe affections a medicine,
called Poudre de Chevalleray, is ufed. It
is diaphoretic antimony, calcined feven times
fucceffively during the fpace of two hours,
with frefh nitre each time, and lixiviated
after each operation. It does not fenlibly
differ from the warned diaphoretic anti-
mony, becaufe the femUmetal, once well
calcined, as it is when detonated with three
times its weight of nitre, cannot be further
calcined, and for that reafon in this prepa-
ration no fucceeding detonation takes place.
The prefent medicine is obferved to be abfo-
lutely ineffectual when deprived of the alkali.
Kermcs mineral is one of the mod valu-
able antimonial remedies we are in pof-
feffion of; it is attenuating, and is employ-
ed with the greateft fuccefs in pituitous
affections of the flomach, the lungs, the
inteftines, and even the urinary paffage. It
is moft commonly ufed in diforders of the
breaft, to afiift expectoration. It ought not,
however, to be adminiftered, till after the
inflammation is abated. It has likewife
great fuccefs when given in repeated fmall
dofes in catarrhs of the breaft,' the humid
afthma, maladies of the fkin, glandular
fwellings, &c. It is adminiftered in a dofe
from half a grain to two or three grains in
proper liquids, or made up in pills. It

fome-

ZINK* 67

fometimes caufes vomiting, and very fre-
quently a&s as a fudorific or a diuretic.

The golden fulphur, on account of its
being a violent emetic and cathartic, is not
much ufed. It was formerly given in the
fame diforders as the kermes, but its effcfts
are much more uncertain.

There are alfo many other preparations
of antimony, which are ufed in medicine
to great advantage; but as they are made
up with vegetable matters, we mail fpeak
of them in another part of this work. This
metallic fubftance is one of the moft im-
portant in the Materia Medica, and phyfi-
cians cannot pay too great an attention to its
properties. It is one of thofe upon which
the alchemifts, and even the chemifts, have
beftowed great labour, which has given rife
to the numerous preparations above de-
fcribed.

CHAP. XIII.
Concerning Zink.

yiNK is a brilliant blueifh white femi-
" metallic fubftance, cryftallized in nar-
row plates. It has neither tafte nor fmell.
It cannot be reduced into powder like the
other femi-metals, but becomes flattened
under the hammer, and may even be lami-

E 2 nated,

68 ZINKU

nated, provided it has not previoufly been
too much hammered. This experiment was
made by Mr. Sage. When it is required
to have zink in a ftate of extreme divifion,
it muft be granulated, that is to fay, poured
melted into cokl water, or elfe reduced into
filings. It has the inconvenience of chok-
ing up the files. Macquer affirms, that
when heated nearly to melting, it becomes
very brittle, and may then be pulverized.
This property is very different from that of
the metals, which become more ductile by
the action of heat, and affords an advan-
tageous procefs for obtaining this femi-
metal in a ftate of extreme divifion. It
may likewife be obtained in this ftate, by
triturating it while melted, and keeping its
particles afunder by continual motion, be-
fore they take the folid form by cooling.
This operation muft not be made in an iron
mortar, becaufe zink always diflblves a por-
tion of this metal ; a mortar and peftle of
marble muft be ufed.

Zink lofes about one feventh of its weight
by immerfion in water. The particular
facets which the pieces of zink met with
in commerce prefent in their fracture, prove
that this femi-metal has the , property of
cryftallizing in a peculiar manner. Mr.
Mongez has fucceeded perfectly in his at-
tempts to obtain this cryftallization. It is
compofed of bundles of fmall quadrangular

prifms,

ZINK, 69

prifms, difpofed in all dire&ions, and of
a blue changeable colour, if expofed to air
while the metal is ftill hot.

Mr. Sage confiders zink as the mod com-
mon of all the metals after iron. He af-
firms, that he found it in all the martial
pyrites ; and Mr. Grignon affirms, that the
cadmia fornacum, obtained from the earthy
ores of iron, contains much zink.

Native zink is very rare; moft naturalifts
doubt whether it exifts at all, yet Mr. Val-
mont de Bomare affirms, that he faw in the
mines of lapis calaminaris, in the dutchy of
Limbourg, and in the mines of Goflar,
fpecimens of this in fmall flexible fibres of
a greyifh colour, and eafily taking fire.

This femi-metal is moft commonly found
in the ftate of calx. It then conftitutes
lapis calaminaris, which has a great variety
of forms. It is fometimes cryftallized in
cubes, in prifms, in leaves, or in plates ->
but moft commonly it is in irregular maffes.
Its colour is likewife fubjecl: to variations.
In fome fpecimens it is white, in others
grey and yellow, and in others reddim.
Though very hard, it is never fufficiently
fo to give fire with the fteel. It is found
in quarries of confiderable extent in the
dutchy of Limbourg, the counties of Na-
mur, and of Nottingham and Somerfet in
England. Marine lubftances, calcareous
fpar, &c. are often met with in calamines,

E 3 which

70 ZINK.

which proves that they have been formed
by a fubfidence from water. The lapis ca-
laminaris is likewife called natural or foffil
cadmia. Bergman, who has made a moft
extenfive inquiry into the analyfis of the
ores of zink, found in almoft all calamines,
filiceous earth, clay, and iron, in different
proportions •> the calamines contain from
four to thirty hundredth parts of metal.

Zink united to fulphur forms blende or
falfe galena. This blende is ordinarily dif-
pofed in fcales. Sometimes it appears cry-
ftallized in cubes more or lefs truncated.
Its colours are various. In fome fpecimens
it refembles that of lead, but moft com-
monly it is black or reddifh. A yellow and
tranfparent fort is found at Ronfberg in
Norway, at Goflar, and Sainte-Mariae. Some
blendes are phofphoric when rubbed in the
dark. There are fome which have this pro-
perty in fo high a degree, that the ftroke
of a toothpick acrofs their fubftance is fuf-
ficient to ihew it. Blende has been called
by the name of fterile nigrum, becaufe when
it has been melted to obtain the lead it ap-
peared to hold, nothing was obtained ; the
zink having been driven offin confequence of
its volatility. All blendes, when rubbed or
diflblved in an acid, give out a very fenfible
fmellof liver of fulphur. Cronftedtconfiders
this ore as zink united to fulphur by the in-
termedium

ZINK. 7I

termedium of iron. Mr. Sage thinks that
it contains an earthy liver of fulphur.

Zink is likevvife found in the fahne ftate
combined with the cretaceous and vitriolic
acids. The firft: of thefe natural com-
pounds is known by the name of vitreous
ore of zink, or zink fpar. This ore is
white, grey, or blueifh ; gives fire with fteel,
is heavy, fometimes cryftallized; alio in fta-
laclites or amorphous ; it diffblves with effer-
vefcence in acids, and affords cretaceous acid.
According to Bergman, one hundred grains
contain fixty-five of calx of zink, twenty-
eight of cretaceous acid, fix of water, and
one of iron.

Native vitriol of zink is found in rhom-
boidal crystals, and in white ftalactites ; it
is often cryftallized in fine needles, or filky
fibres, refembling amianthus. In this ftate
it is called plume-alum. It is found in
Italy, and in the mines of Goflar, in the
Hartz. The zink ores may be difpofed in
the following manner, according to the
(late in which the femi-metal exifts.

STATE I.

Native Zink in flexible, greyifli, and
inflammable Fibres.

E 4 STATE

72 2INK.

STATE II.

Calx of Zink j Calamine.

Varieties.

i. White calamine, in fhort tetrahedral
prifmatic cryftals, grouped confufedlyj it
fometimes is greenifh.

2. Calamine cryftallized in pyramids fimi-
lar to the dog's-tooth-fpar, of a white grey,
greenifh, or reddifh colour. Meffrs. Sage,
and Rome de Lifle think, that while this
calamine is depofited, the calcareous fpar is
decompofed ; it is often found, in fadt,
partly calcareous, and hollow in its inter-
nal parts.

3. Calamine folid, and, as if worm-
eaten; it is furrowed, cellular, and cryftal-
lized, as it were, in dendrites.

4. Compadt and folid calamine ; lapis ca-
laminaris. That which is obtained from
the county of Namur is always calcined ;
it is not allowed to be exported, without
previoufly fubjedting it to this operation.

5. Calamine in greenifh or yellowifh fta-
lagmites.

6. Zeolitiform calamine, known by the
name of zeolite of Friburg. Mr. Pelletier
has difcovered, that this pretended zeolite,
of a pearl colour, contains in one hundred
parts, from forty-eight to fifty-two, of

quartz,

zink. 73

quartz, thirty-fix of the calx of zink, and
eight or twelve of water.

STATE III.
Zink mineralized by Sulphur ; Blende.

Varieties.

i. Grey blueifti blende, with a metallic
afpecft, cryftallized in cubes or rhombufes,

2. Black cryftallized or irregularly formed
blende.

3. Red or brown reddifh blende.

4. Phofphoric blende, green, yellowifh,
or red.

5. Yellow greyifti blende, mixed with
galena and petroleum.

6. White blende.

7. Yellow blende of a wax colour.

8. Blende in a ftate of decompofition,
whofe laminae are feparated,' and their bril-
liancy deftroyed. It pafles to the ftate of
calamine.

STATE IV.

Saline Zink.

Varieties.

1. Spathofe zink, or vitreous ore of zink*

2. Vitriol of zink in rhomboidal cryftals,
in ftaladites, or in fibres of a filky appear-
ance.

To

74 ZINK.

To make an aflay of calamine, nothing
more is neceflary in genera], than to pulve-
rize and mix it with charcoal, and to heat
it in a crucible covered with a plate of cop-
per ; the latter becomes yellow, and is
converted into brafs, Bergman has made
a much more perfedt analyiis of calamines
by the humid way. He applied the vitrio-
lic acid to decompofe pure calamines, and
the zink fpar, The folution contained vi-
triol of zink, and vitriol of iron, He de-
compofed the latter by a known weight of
zink, and precipitated the decanted fluid by
mild mineral alkali. He finds, by experi-
ment, that one hundred and ninety-three
grains of this precipitate contain one hun-
dred grains of zink. From the weight of
the precipitate he deducts the weight of the
zink employed to precipitate the iron.

Moft calamines being more compounded
than thofe here mentioned, and containing
quartz, clay, and chalk, combined with the
calces of zink, iron, and even lead, Berg-
man firft treats them three fucceffive times
with twice their weight of nitrous acid each
time. By heating the mafs to drynefs, the
acid calcines the iron, and renders it info-
luble. He afterwards diflblves the foluble
part in additional nitrous acid, the iron, the
quartz, and the clay remaining behind.
The acid takes up the calcareous earth, the
calces of zink and of lead : marine acid is

employed

ZINK, 75

employed to precipitate the latter ; the vi-
triolic acid to feparate the calx; and the
zink is la it of all precipitated by the Pruf-
fian alkali. The fifth part of the weight?
of this precipitate, he takes to exprefs the
zink contained in the calamine. He like-
wife employs a fccond method; vitriolic
acid is diitilled from calamine to drynefs,
the refidue is afterwards lixiviated in warm
water; from this lixivium he precipitates
the iron and clay, by cauitic volatile alkali;
the zink remains fufpended in the folution
of vitriolic ammoniac.

Theaffay of blendes, after previous roaft-
ing, was formerly made in the fame manner
as calamines ; Mr. Monnet is the firit who
affirmed that they might be conveniently af-
fayed by folution in aqua fortis, which unites
to the metallic fubftance, and feparates the
fulphur. The calx of zink is feparated
from the nitrous acid by diftillation. Berg-
man has made the fame accurate experiments
en thefe ores as on the calamines, and has
greatly improved on Monnet's method of the
humid analyfis. He firit feparates the water,
the arfenic, and part of the fulphur they
contain, by diftillation ; next he treats them
with different acids, accordingly as thefe act
more or lefs upon their contents, and preci-
pitates the folutions by different re-agents.
The ores of zink are not worked for the pur-
pofe of gaining the femi-metal. It is ob-

ferved,

76 ZINK.

ferved, during the fmelting of lead ores mix-
ed with blende, that the zink is fublimedin
the chimnies of the furnaces, in the form of
calx, and produces greyifh incruftations,
named tuttia, or cadmia fornacum. Ano-
ther portion is obtained in the metallic form,
by cooling the anterior part of the furnace.
The zink being driven up in the vapourous,
form by the action of the fire, is condenfed
in this place, and falls in fmall grains into
powder of charcoal, which covers a ftone
placed below. The femi-metal is preferved
from calcination by the powder of charcoal,
and is afterwards melted in a crucible, and
run into moulds. Such is the procefs by
which the greater!: part of the zink found
in commerce, is obtained at Rammelfburg,
whether in the ftate of calx or metal. This
zink is always united to a certain quantity
of lead ; it feems that the zink prepared in
China, which comes to us under the name
of tutenag, is much purer *, but the man-
ner of preparing it is unknown. Mr. Sage
affures us, that the English obtain zink in
the large way, from lapis calaminaris, by
diftillation, but that their apparatus is kept
a fecret.

* Mr. Ki: wan gives the name of tutenag to a variety
of the brittle calamine of China, which was analyfed by
Mr. Engeftrom, for which fee the Memoirs of the Aca-
demy of Stockholm, for the year 1775. This ore is very
rich, and contains from 7%% to tVe zink.

Zink

ZINK. J7

Zink expofed to heat in clofe veffels,
melts before ignition, and is volatilized
without decomposition. If it be fuffered to
cool flowly in a veffel, by which the melted
portion of the femi-metal can be fuffered to
run out, the remainder of the zink is found
cryftallized in needles, or flender prifms.
Mr. Mongez, for this purpofe, ufes a veffel
pierced at the bottom and at its fides, with
a number of holes which he flops with earth
of bones. When the zink cools at its fur-
face, the holes are to be opened gradually,
and the metal agitated by a red hot iron,
introduced through one of thefe openings.
This fimple procefs occafions the melted
portion of the zink to run out ; the veffel is
then to be (hook, till no more melted metal
runs out, and the cold portion cryftallizes.
If it be left in the veffel, it retains its me-
tallic colour, but if it be expofed to air, it
takes a tarnifh of rainbow colours. When
zink is melted with contact of air, it be-
comes covered with a grey pellicle, which
is quickly converted into a yellowifh earth
or calx, and eafily reducible. This calx
weighs more than the zink made ufe of,
but if the femi-metal be ftrongly heated,
it burns with a white, or light greeniih yel-
low flame, very brilliant, and fimilar to that
of phofphorus. The current of this flame
drives up the calx of zink, which is con-
denfed in the air in the form of white, and

very

78 ZINK.

very light flocks, named flowers of zink,
pompholix, nihil album, philofophical wool,
or cotton. It is a perfect calx of zink, and
weighs more than the femi-metal made ufe
of to form it ; Mr. Baume having obtained
from each pound of zink, fixteen ounces,
fix drachms, fifty four grains of flowers.
It is not volatile, its fublimation being pro-
duced only by the rapidity with which the
zink burns ; it confequently remains very
fixed when expofed to heat alone in a cruci-
ble. It preferves for a certain time a phos-
phoric light, fenfible in the dark. It may
be fufed into glafs, by a mod violent heat;
the glafs of zink has a beautiful yellow
colour.

The calx and the glafs of zink, are no-
thing more than the femi-metal combined
with the bafe of vital air. The glafs does
not appear to differ from the white calx,
but by the more intimate union of the two
principles. ' This compound is among the
number of metallic calces which heat cannot
deftroy, and are not reducible without ad-
dition. Its decompofition cannot be effect-
ed, unlefs it be heated in contact with com-
buftible bodies. A mixture of pompholix
and charcoal being ftrongly heated, zink is
obtained, and the charcoal is found to be
partly burned, by virtue of the oxigynous
principle it has taken from the metallic
calx. Zink has therefore lefs affinity with

the

zink. 79

the bafe of air than charcoal has, though it
feems to be more combuftible. This ope-
ration does not fucceed well, but in clofe
vefTels, and for that reafon the Englifh are
faid to reduce lapis calaminaris by diftilla-
tion.

Zink is fcarcely alterable by the air. Its
furface tarnilhes a little, and appears to fuf-
fer a flight beginning of calcination.

Water has a ftrong action on zink 5 when
this femi-metal begins to be red hot, it is
then eafily calcined, and a large quantity of
inflammable gas is given out; a proof that
the water is decompofed by the zink, which
feizes its oxigynous principle. MelTrs. La-
voifier and Meufnier have afcertained this
fact in their experiments concerning the de-
composition of water.

Zink has no action on the verifiable and
argillaceous earths, but its calx enters into
vitreous. compounds, and colours them yel-
low.

Ponderous earth, magnefia, and lime, have
no action on zink.

The cauftic vegetable, and mineral alkalies,
being boiled on this femi-metal, turn its
furface black, and themfelves acquire a dirty
yellow colour, by holding in folution a cer-
tain quantity of zink. This may be fepa-
rated by acids, as Mr. De LafTone has fhewn.
The volatile alkaline fpirit acts lefs ftrongly
on zink when heated, no doubt on account

of

80 ZINK.

of its volatility ; but by cold digeftion it
diffolves a fmal] quantity. In thefe three
folutions, a certain quantity of inflammable
gas is difengaged, the production of which
appears to be due to the water. So that it
is this fluid which adts on the femi-metal,
calcines it, and renders it partially foluble
in alkalies.

The vitriolic acid diluted with water,
diflblves zink in the cold. In proportion as
the acid exerts its aftion, the femi-metal
becomes of a blackifh grey, much heat is
produced, and a black powder is precipitat-
ed, which has not yet been well examined.
A large quantity of inflammable gas is dif-
engaged, which burns with a very bright
flame, and detonates with pure air. This
elaftic fluid, whofe fmell is fimilar to that
of the gas obtained during the folution of
iron by the fame acid, is certainly produced
by the water ; for oil of vitriol does not dif-
folve zink, without the afliftance of heat,
and then produces only fulphureous gas.
The water therefore begins the calcination
of the zink, and the acid afterwards dif-
folves the calx. When no more inflam-
mable gas is difengaged, the efFervefcence
ceafes, the fmell changes, and perfectly re-
fembles greafe beginning to be rancid. The
liquor is whitifh, and rather cloudy, but
becomes tranfparent when diluted with
water. It affords a white vitriol by evapo-
ration,

ZINK. 8l

ration, rather more foluble in hot than in
cold water, and of which a portion cryftal-
lizes by cooling. Very regular cryftals of
vitriol of zink are eafily obtained by expo-
fing for fome days to the air a folution of
this fait made in boiling water, and a little
evaporated : tetrahedral prifms are then
formed, terminated by pyramids of four fides :
the fides of thefe prifms are fmooth. This
form was pointed out by MefTrs. Sage and
Rome de Lille, and I have myfelf remarked
it. Mr. Bucquet has obferved, that thefe
prifms were rhomboidal. Mr. Monnet
however affirms, that this fait cryftallizes
with great difficulty, and requires much
evaporation, and fudden cooling, to afford
regular cryftals without confidence. The
white calx, or flowers of zink, likewife dif-
folve in the vitriolic acid, and afford white
vitriol.

This fait has a flrong ftyptic tafte. *Ac-
cording to Hellot, it lofes a part of its acid
by the a&ion of fire. This acid has the ful-
phureous charadters, and becomes hot with
oil of vitriol, according to the obfervations of
Macquer. Vitriol of zink is not much
changed by expofure to air, when it is very
pure. It is decompofable by lime, and by
the different alkalies. The calces of zink,
precipitated by thefe fubftances, may be
re-diffolved in acids, and even in alkalies.
The volatile alkali becomes of a dirty brown
Vol, III. F colour,

82 ZINK.

colour, after diffolving it. The vitriol of
zink decompofes nitre, and is itfelf de-*
compofed. By diftilling this mixture, two
kinds of nitrous acid, which do not mix,
are obtained, together with the glacial oil of
vitriol ; we fhall fpeak more fully on this
fubjecl: at the article of martial vitriol.

A vitriol of zink, prepared in the large way
at Collar, is met with in commerce under the
nameof white vitriol. Itismadethus: blendes
are roafted ; a portion of the fulphur burns, and
furmihes vitriolic acid, which diffolves the
calx of zink. The roafted ore is then wafh-
ed, and the lixivium being decanted, is ex-
pofed to evaporation, and affords cryftals.
The fait being melted by a gentle heat, fo as
to deprive it of its water of cryftallization,
and then fufFered to cool, becomes conden-
fed into white, opake, and granulated mafles,
refeniblingfugar. The vitriol of Goflar,when
diflblved in boiling water, cryftallizes by
cooling. Its cryftals are fomewhat reddifh, a
circumftance to be attributed to the impu-
rities of the fait, which is fuppofed to con-
tain a fmall quantity of lead and iron. To
purify it, zink may be thrown into its folu-
tion. The femi-metal precipitates the iron
and the lead, becaufe it has a ftronger affi-
nity with the vitriolic acid -, and the liquor
being filtrated, is confequently found to
contain pure vitriol of zink. There is ftill
greater reafon to think, that the impurity

of

ZINK. 83

of the vitriol of Goflar confifts in iron, from
the circumftance of the zink met with in
trade being magnetical, doubtlefs becaufe it
contains iron. Experiments concerning this
fcmi-metal ought therefore not to be made,
but with zink prepared by reducing the pre-
cipitate of white vitriol purified in the man-
ner here (hewn . We mud however obferve,
that zink is very often magnetical only at
that part of the piece which has been cut
with fciffars, or iron wedges.

The diluted nitrous acid combines very
rapidly with zink, without the affiftance of
external heat. A confiderable heat is pro-
duced in this folution, as well as in that
wherein the vitriolic acid is ufed. The ef-
fervefcence, which accompanies this combi-
nation, is occafioned by the difengagement
of a large quantity of nitrous gas, which fud-
denly grows red by mixing with the air,
when the operation has been performed in
an open veflel, but which is colourlefs, and
may be confined over water, by plunging the
extremity of the veffel containing the mix-
ture, underneath the orifice of a glafs con-
taining that fluid. This experiment (hews,
that zink decompofes the nitrous acid, and
deprives it of a portion of its oxigynous
principle. If the zink be mixed with a por-
tion of iron, it is covered with a reddifh
ochreous powder, which is merely a portion
of that metal calcined by the acid. If it be
F 2 pure,

84 ZINKi

pure, certain flocks of a blackifh matter are
precipitated, as is obferved with the vitrio-
lic acid. The nitrous acid holds a much
larger quantity of zink in iolution, than
the vitriolic. Mr. Bourne affirms, that fix
ounces of this acid diffolved five drachms
and a half of zink, in lefs than two hours.
The nitrous folution of zink is of a greenifh
yellow, and not perfc&ly clear when newly
made, but it lofes this colour, and becomes
tranfparent, after ftanaing for fome time.
It is very caufiic, and quickly corrodes the
fkin, though made with an acid diluted
with water. I have obtained, by evapora-
tion and cooling, cryftals in tetrahedrai
ftriated flat prifms, terminated by pyramids
of four fides likewife ftriated. The nitre
of zink being put on hot coals, firft melts
and detonates as the portions become dry,
and the detonation is attended with a fmall
reddifh flame. The fame phenomenon does
not appear, when the fufion is performed in
a crucible. It cannot be dried, even by the
mildeft heat, without alteration ; vapours of
nitrous acid in this cafe efcape,and itbecomes
of a brown red, and of the confiftence of a
jelly. If it be fuffered to cool in this ftate,
it preferves its foftnefs for fome time; but
if it be kept heated for a fufficient time, it
dries entirely, and leaves a yellowifh calx.
HelSot has obtained from the diftillation of
nitre of zink, a very fuming acid, and ob-»

ferved

ZINK. 85

ferved the red colour it a flumes in melting.
The nitre of zink quickly attrafts humidity,
and lofes its reeular form aft^r fome days
expofure to the air, nothing remaining but
ftriated and pointed prifms, whofe figure can
fcarcely be determined. It is not known
whether it is decompofable by other acids.
Meflrs. Pott and Monnet affirm, that zink
has a ftrong affinity with all thefe falts,
without having any preference for any one in
particular. The flowers of zink form abfo-
lutely the fame fait with the nitrous acid,
according to Hellot.

The muriatic acid ads on zink as ftrong-
ly as the nitrous. During the rapid eflfer-
vefcence which accompanies this combina-
tion, much inflammable gas is difengaged,
which has the fame properties as that afford-
ed by the nitrous acid ; and this laft is
known to confifl: of water decompofed by
zink. Black flocks are gradually depofited,
which fome have confidered as fulphur,
others as iron, and Mr. Laflbne thinks to
be a calx of zink. This matter diflblves in
acids ; is not reducible to the metallic ftate,
and becomes calcined on hot coals. Mr.
Monnet thinks that it arifes from certain
foreign metallic fubftances, as for example,
iron and copper, which are often found in
zink. It certainly deferves to be more par-
ticularly examined. The folution of zink by
the muriatic acid, is colourlefs, and does
F 3 not

36

ZINK

not afford cryftals by evaporation ; when
heated it becomes of a blackifh brown, emits
acrid and penetrating vapours of marine
acid, and becomes thick. Expofed to the
air for eight days in this ftate, it affords no
cryftals. By diftillation it gives out a fmall
quantity of very fuming acid, and a true
butter of zink. Meffrs. Hollet and Monnet
have defcribed this experiment very accu-
rately; I have repeated it many times in
my courfes of lectures, and obtained a fmall
quantity of yellowifh acid, which was fuc-
ceeded by a congealed matter in the neck of
the retort. This butyraceous fubftance was
was of the fineft milk-white colour, very
folid, and formed of fmall radiated needles,
in the manner of a ftalactite. It is fufible
by a gentle heat. I have preferved it for
feveral" years in well-clofed veffels of glafs.
It has attracted very little moifture ; the
part which touches the glafs is yellowifh, and
the bottom of the bottle prefents rainbow
colours. This alteration doubtlefs depends
on the action of light. There remains in the
retort, which is ufed for this diftillation, a
blackifh vitriform and deliquefcent matter.
The butter of zink, which Hellot obtained,
was blackifti -, he fays, that the vitriolic acid
difengages the muriatic. The calx of zink
has the fame habitude with this acid.

The cretaceous acid fpirit in which zink
or its calx are digefted in the cold, diffolves,
at the end of twenty-four hours, a confider-

able

ZINK. 87

able quantity, according to Bergman. This
foliation, when expofed to the air, becomes
covered with apellicle,which refle&s various
colours, and is merely a chalk of zink, cal-
led aerated zink by that celebrated chemift.

The acftion of the fluor and boracic acids
on zink are not known.

All the folutions of zink in acids are
precipitated by lime, magnefia, the fixed and
volatile alkalies. The calx of this metal
then appears in the form of white or yellow-
i(h flocks, according to the Rate of their fo-
lution, or the purity of the precipitant.
This calx is reducible by the addition of
combuftible matters, is foluble in acids and
in alkalies, either fixed or volatile. When
more of the latter is added than is neceffary
to difengage the calx of zink, the precipi-
tate difappears by degrees, and the liquor
aflumes a dirty yellow colour, which indi-
cates the folution of the calx of zink in
the alkali. When, inftead of pure and cauf-
tic alkalies, the cryftals of either the veget-
able, mineral, or volatile alkali are ufed, the
erfervefcence is very inconfiderable, the pre-
cipitate is white, and it is found, that the
cretaceous acid unites with the calx, fo that
in thefe cafes, two dccompofitions, and two
new combinations are effected.

Zink has the property of decompofing

feveral neutral falts. If it be treated in the

dry way, with vitriolated tartar in a cruqi-

F 4 ble,

88 ZINK.

ble, it decompofes the fait, and forms a
liver of fulphur, in the fame manner as
regulus of antimony does. In this experi-
ment the zink feizes the oxigynous princi-
ple of the vitriolic acid, and the acid pafles
into the ftate of fulphur, which the alkali dif-
folves. The hepar, formed by this combi-
nation, difiblves a portion of the calx of
zink. All the vitriols are likewife decom-
pofed by zink.

This metal, in filings, or in powder, caufes
nitre to detonate with Angular rapidity.
The mixture being very dry, and thrown by
fpoonfuls into a red-hot crucible, produces
a white and red flame. The activity of the
inflammation is fuch, that portions of burn-
ing matter are thrown to a diftance out of
the crucible, in fuch a manner as to require
fome precaution on the part of the opera-
tor. The zink burns by the afiiftance of the
pure air afforded by the nitre, and is after-
wards found in a calciform ftate, more or
lefs perfect, according to the quantity of
nitre ufed. One part of the refidueis folu-
ble in water. It confifts of the alkali com-
bined with a portion of the calx of zink,
which may be precipitated from its folution
by the addition of acids. Refpour attribut-
ed to this folution the property of diflblving
all the metals, if Hellot may be credited,
who gives it as the alkaheft of that alchemift.

Zink,

ZINK. 89

Zink, according to the experiments of
Pott, appears capable of decompofing marine
fait. It efpecially decompofes fal ammo-
niac with great facility. Mr. Monnet af-
firms, that this femi-metal triturated with
fal-ammoniac, difengages the volatile alka-
li. Bucquet has obferved, that when fal
ammoniac and zink are diftilled together,
alkaline gas and inflammable gas are pro-
duced by the combination of the marine acid
with the femi-metal: and he was feniible
that the facility with which the zink dif-
engages the volatile alkali, is a confequence
of its ftrong action on the acid. The calx
of zink likewife difengages it according to
Hellot. The reiidue of this decompofition
is muriate of zink, which may be fublimed
into butter of zink.

When a folution of alum is boiled with
filings of zink, a decompofition takes place,
which affords white vitriol. The bafe of
this fait therefore feems to have a weaker
affinity than zink with the vitriolic acid.
This fact was obferved by Pott, and we fhall
have occafion to make the fame remark with
regard to many other metallic fubftances.

The effects of inflammable gas on zink
have not yet been examined. I have only
obferved, that this femi-metal, plunged in
inflammable gas, aifumes, after a certain
length of time, a beautiful blue and change-
able colour 5 but I have not followed this

alteration

90 ZINK.

alteration any further. It does not feem
capable of reducing the calx of this femi-
metal, which retains the oxigynous prin-
ciple with great force.

Zink does not appear to combine with
fulphur, but with the greatefl difficulty.
When thefe two fubflances are melted to-
gether, they remain diftinct, without con-
tracting any kind of union. Mr. Dehne,
however, obferved, that if they be kept
for a certain time in fulion together, the
zink is partly calcined, afTuming at the
fame time a brown or greyifh colour, and
becoming much heavier. Mr. de Morveau
difcovered, fince the time of the remark of
Mr. Dehne, that the calx of zink unites eafily
with fulphur by fufion, and that a grey
mineral is produced very fimilar to the
blende of Huelgoet, from which yellow and
prifmatic needles are fometimes fublimed,
and fix themfelves to the cover of the cru-
cible. Mr. de Morveau obferves, that it is
flill more probable that blende is naturally
formed by the combination of the calx of
zink and fulphur, as native zink has never
yet been found.

Mr. Malouin has not fucceeded in his
attempts to combine zink with the alkaline
liver of fulphur, whether by the humid,
or by the dry way, or by varying the pro-
portions of thefe two fubflances to each
other.

The

ZINK. 91

The fame chemift combined zink with
regulus of arfenic. He obferved, that this
regulus does not unite fo well with zink,
as with the calx of arfenic -, neverthefs, in an
experiment, wherein he diftilled a mixture
of this calx with tallow and zink, he obtain-
ed a blackifh mafs reiembling blende, but
lefs confident. It likewife appears that the
zink feizes the vital air of the calx of the ar-
fenic when they are dirtiiled together, and
that a portion of this femi-metal aflumes the
ftate of flowers, at the fame time that a por-
tion of the arfenic is revived. A feries of
experiments, made with a view to difcover
the reciprocal adion of metallic calces and
metals on each other, and to determine the
elective attractions of the oxigynous prin-
ciple with thefe fubftances, could not fail
of proving highly inftructive.

It is not known whether zink is capable
of being alloyed with cobalt.

It does not combine with bifmuth, and
when thefe two femi- metals are fufed to-
gether, the bifmuth takes the lower place
on account of its greater weight, and they
may be feparated by a ilroke of the ham-
mer.

Zink, fufed with regulus of antimony,
affords a hard and brittle alloy, which Ma-
louin limply mentions, without pointing
out any of its other properties.

Zink is of great ufe in the arts. It is

employed

92 ZINK.

employed in many alloys, efpecially in tom-
bac, prince's metal, and the various kinds of
bn.fs. Fine filings of zink are ufed to pro-
duce the whiteand brilliant ftars in fire-works.
Some perfons have propofed to fubftitute this
femi-metal infteadof tin for lining copper vefr
fels ; the latter metal having been fuppofed
to be infufncient to prevent the dangerous
effects of that metal, Malouin, after having
compared thefe metallic fubftances in Two
Memoirs, printed among thofe of the Royal
Academy of Sciences, for the years 1743
and 1744, gives an account of the experi-
ments made by him refpetting the lining
of veffels with zink. From his refearches
it appears, that this lining fpreads more
evenly on the copper, is much harder,
and lefs fufible than that of tin, and coiit
fequently more durable, and lefs fubjecl: to
leave the copper uncovered. Macquer, who
acknowledges thefe advantages, has how-
ever made feveral very important obferva-
tions concerning the ufe of zink for cu-
linary veffels, and thinks it dangerous, be-
caufe it is foluble in vegetable acids, fuch
as vinegar, verjuice, &c. and has a confi-
derable emetic power. Fie proves this by
the vitriol of zink, which was formerly
employed as a vomit under the name of gilla
vitrioli, and by the teftimony of Gaubius,
who mentions a celebrated remedy for con-
yulfive diforders, named Luna iixata Lude-

manni,

sink, 93

trianni, which Macquer afferts to be the
flowers of zink. This pretended luna fix-
ata was flrongly emetic in very fmall dofes.
But may it not be prefumed that thefe
objections, which are applicable only to
the vitriol and the flowers of zink, cannot
be applied to the femi-metal itfelf, nor
even without further experiments to the
falts formed by its combination with vege-
table acids. Mr. de la Planche, doctor in
medicine of the faculty of Paris, has changed
this prefumption into certainty, by expe-
riments made with great care on himfelf.
He took the falts of zink, formed by the
vegetable acids, in a much flronger dofe than
the aliments prepared in copper tinned with
zink can poffibly contain them, and no
dangerous effect followed the uie of thefe
compounds. However, fince objects which
relate to the health and the lives of man-
kind, cannot be treated with too much
circumfpection, it appears to me to be pru-
dent and even neceffary not to decide on
this fubject, till after a great number of
experiments have been made concerning the
nature of zink, and the black matter which
feparates during the folution of this femi-
metal in acids, and which not being well
known, may itfelf contain certain noxi-
ous fubftances; and efpecially till it has
been well eftablifhed by a great number of
experiments, what the action of zink and

its

94 MERCURY.

its falts, formed with the vegetable acids
employed in cookery, is upon the animal
oeconomy.

The German phyficians employ the flow-
ers of zink with fuccefs as an antifpafmodic
in convulfions and epileptic fits. It is not
much ufed in France, yet it appears that
this remedy might be ufefully adminiftered
in pills in the dofe of half a grain each day.
I have been afiured, that a much more con-
fiderable dofe has been taken at Edinburgh
without any fenfible effedt. This fad is
contrary to what Gaubius afferts concerning
the emetic property of this calx of zink.
Pompholix, tutty, &c. are ufed as excellent
deficcative medicines, to be externally ap-
plied in diforders of the eyes.

CHAP. XIV.
Concerning Mercury.

Ti/rERCURY or quickfilver has the opa-
■*■*■*■ city and brilliancy of metals, and next
to gold and platina is the moft ponderous fub-
ftance we know : a cubic foot of pure mer-
cury weighs 947 pounds; it lofes by immer-
lion in water one thirteenth of its weight.
As it is continually fluid, its tenacity and
ducflility are not well known, and it ftill re-
mains a queftion among what fpecies of

metallic

MERCURY. 95

metallic bodies it ought to be placed. Like
the femi-metals, it is volatile. It has a.
kind of duftility, refembling the metals ;
but its extreme weight, its habitual fluidity,
its volatility, and the Angular alterations it
is capable of undergoing in many combi-
nations, feem to juftify the ranking it as
a peculiar fubftance, which feems to belong
to the metallic matters only by its brilliancy,
weight, and combuftibility : we fhall there-
fore place its hiftory between that of the
femi-metals and themetals. It was long taken
for granted, that mercury could not be de-
prived of its fluidity; but the academicians of
Peterfburg have proved the contrary. Thefe
learned men availed themfelves of the ex-
ceflive cold in the year 1759, to try many
important experiments. They increafed
the natural cold by the affiftance of a mix-
ture of fnow and fuming fpirit of nitre,
and by that means fucceeded in caufing a
mercurial thermometer to fall to 2 1 3 degrees,
according to the graduation of De Lille;
which anfwers to 46 degrees below freez-
ing of the gradation of Reaumur. Thefe
philofophers, oblerving that at this degree
the mercury defcended no longer, broke the
ball of glafs, and found the metallic fluid
frozen, in the form of a folid, which, on tri-
al, proved capable of extenfion under the
hammer. This experiment demonftrated
that mercurv, like all other metallic fub-

fiances,

96 MERCURY.

fiances, is capable of afTuming the folid
form, and that it is then in a certain de-
gree ductile. They could not determine
the degree of ductility it is fufceptlble of,
becaufe every ftroke of the hammer com-
municating heat to fome part of the metal,
melted it, and caufed it to flow in that
point.

Mr. Pallas, who fucceeded in congealing
mercury in the year 1772, at Krafnejark,
by the natural cold of 55 degrees and an
half, obferved, that it then refembled foft
tin, and was capable of being beat out into
plates, that it broke eafily, and that the
pieces being brought together united again.
In the year 1775 Mr. Hutchins obferved
the fame phenomenon at Albany fort, and
Mr. Bieker at' Rotterdam in 1776, at the
fifty-fixth degree below Zero. Laflly, this
congelation was effe&ed in the year 1783,
in England, at a more moderate degree of
cold; and it was determined that 32 degrees
below Zero of the thermometer of Reaumur,
is the term at which this congelation takes
place. If therefore the mercury defcended
lower in the early experiments, the phe-
nomenon muft be attributed to the conden-
fation of the folid metah Hence we fee,
that this , metal is the moft fufible of any
we know. The greateft cold known in
the countries from whence it is obtained,
cannot render it folid. It is probable, that

if

MERCURY. 97

if in the preceding experiments, the cold
by which the mercury was frozen had been
produced by infenfible degrees, that me-
tallic fubftance would have taken a regular
cryftallized forrr^*.

The habitual fluidity of mercury has
caufed it to be^efleemed a peculiar metallic
matter, and it has been called aqua non
madefaciens manus, water which does not
wet the hands. It is true* that mercury
does not wet the hands, nor moft of the
other bodies which may be wetted by water,
oils, and other liquids ; but this phenome-
non depends only on the fmall. degree of
affinity which exifts between that metallic
fluid, and the bodies themlelves ; for when
it is in contadl with iubftances with which it
can unite, as gold, Giver, tin, &c. it becomes
clofely united to them, and wets them
in fuch a manner, that they cannot be dried
again, but by evaporating the mercury
which adheres to them.

Mercury being a melted metal, always
affects the form of glubules when it is di-
vided ; and when it is confined in a bottle,

* The reader will find an hiftory of the congelation of
mercury, written by Dr. Blagden, in the Philofophical
Tranfactions for 1783, Part 2. Hutchins's experiments
made at Hudfon's Bay, together with Mr. Cavendifh's
obfervations thereon, are likewife inferted in the fame
volume. T.

Vol. III. G its

98 MERCURY.

its furface appears convex. This effeft de-
pends both on the fmall degree of affinity
which mercury has with glafs, and the
ftrong attraction that tends to bring the
parts of this metal together ; for if the
fluid be placed in a metallic verTel with
which it has an affinity, its furface then
appears concave, like that of other fluids,
becaufe it combines with the fides of the
veffels.

Mercury has no tafte that the nerves of
the tongue and palate can perceive, but it
produces a very evident effect on the fto-
mach and inteftines, as well as on the fur-
face of the {kin. Infects and worms are
infinitely more fenfible of this tafte than
other animals, and for that reafon it very
foon kills them ; and phyficians adminifter it
as an excellent vermifuge. It is by virtue
of this property likewife that it cures the
itch, and other cutaneous diforders, which
many philofophers have thought to be
produced by certain infedts, which pe-
netrate the texture of the fkin. But this
opinion has not been generally adopt-
ed, though feveral naturalifts have de-
fcribed the animal, which caufes the itch,
&c.

Mercury rubbed for a fhort time between
the fingers emits a flight peculiar fmell.
When it is very pure, and is agitated, it is

fometimes

MERCURY. 99

fometimes obferved, more efpecially in hot
weather, to fhine with a fmall phofphoric
light clearly difcernible. This phenome-
non has been ihewn with the mercury
of the barometer by feveral natural phi-
lofophers *. If the hand be plunged in
this metallic fluid, a fenfation of cold is
perceived, which feems to fhew that its
temperature is much beneath that of the
atmofpheric air j yet by plunging a ther-
mometer in the fame mercury, it is imme-
diately feen that their temperatures do not
differ. Does not this erFecl, which deceives
us, and entirely depends on our fenfations,
arife from the great weight of this metallic
fubftance ? or is it produced by an increafe
of the evaporation of the fluid, which is
continually emitted from the pores of the
fkin f ?

* This phenomenon is produced by the efflux of the
ele&ric fluid into the vacuum over the mercury ; that fluid
being difengaged by the friction between the non-ele&ric
mercury, and the electric glafs. T.

t The temperature of the animal being always higher
than the common temperature of the atmofphere and of the
mercury, the animal muft of courfe be cooled by the mer-
cury, at the fame time that the mercury is rendered warm-
er. The large mafs or denfity of the mercury, will caufe
the mean temperature to be nearer its original tempera-
ture, than a lighter fluid in the fame cafe would have
done j that is to fay, the mercury will cool the animal
more. It is befides an excellent conductor of heat. T.

G 2 Mercury

R C U R Y ,

'divided by continual agi-
xiat of the fails of a mill,
;rees into a very fine black
Ethiop's per fe, by reafon
lour. The mercury is not chan-
ged in this experiment, and by a flight heat,
or by trituration in a warm mortar, it may
be made to refume its ufual fluidity and
brilliancy.

Mercury is not found abundantly in na-
ture. It is met with in the earth, either in
the virgin ftate, pofleffing all its ufual pro-
perties, or combined with acids, fulphur, or
other metallic matters in the mineralized
ftate.

Running mercury is found in globules,
or larger maffes, in friable earths and ftones,
and moft commonly exifls in the clefts or
cavities of its ores. At Idria, in Spain, and
in America, it is colled:ed in the cavities and
clefts of rocks. It is likewife found fome-
times in clay at Almaden, and in beds of
chalk in Sicily. Laftly, it is found in filver
and lead ores, and mixed with white arfenic.

Mr. Sage mentions an ore of mercury, in
the calciform ftate, at Idria, in Friuli ; it is
of a brown red, very foft, and granulated
in its fradture ; fome globules of running
mercury exift in it, and it is reducible by
mere heat, without addition. Mr. Kirwan
confiders it as the combination of mercurial

calx

[ERCUHY. 101

calx and cretaceous acid ; one hundred parts
of the ore afford ninety-one parts of mer-
cury.

In the year 1776, Mr. Woulfe found at
Obermufchel, in the dutchy of Deuxponts,
a cryftallized, ponderous, fpathofe, white,
yellow, or greenifh ore of mercury, in which,
by means of alkalies, he difcovered the pre-
fence of the vitriolic and muriatic acids.
It is a compound of vitriol of mercury, and
corrofive fublimate. Mr. Sage affirms, that
it contains eighty-fix parts of mercury in
the hundred. This chemift has defcribed a
corneous brown ore of mercury, from Ca-
rinthia. Mercury is moft commonly found
naturally combined with fulphur ; it is then
known by the name of cinnabar. This mi-
neral fubftance is red, and has not a me-
tallic appearance, though the quantity of
fulphur is but fmall in companion to the
mercury; a proof that the combination of
thefe two bodies is very intimate. Cinna-
bar is found in the dutchy of Deuxponts, in
the Palatinate, in Hungary, in Friuli, and
Almaden in Spain, and in South America,
efpecially at Guamanga in Peru. It is
fometimes compact, and its colour varies
from a pale red, to a deep and blackifh red.
Sometimes it is found in tranfparent ruby-
coloured cryftals, and often in a kind of
icales, or flattened laminae. It is called native
Vermillion, and cinnabar in flowers, when

G 3 it

102 MERCURY.

h is in the form of a very brilliant red pow-
der. Laftly, It is found difperfed with dif-
ferent earths in felenite, mixed with iron,
with pyrites, and with filver.

Mr. Cronfledt in his mineralogy, fpeaks
of an ore of mercury, in which that fub-
ftance is united to fulphur and copper ; it
is of a blackifh grey, brittle and ponderous ;
its frafture is vitreous, and it decrepitates in
the fire. It is found at Mufchel Lanfberg.

The fame mineralogift affirms, that mer-
cury amalgamated with virgin filver, has
been found in the mine of Sahlberg in Swe-
den. Rome de Lifle has in his cabinet
a piece which he thinks to be of this
fpecies.

Mr. Monnet, in his fyftem of mineralo-
gy, fpeaks of an ore brought from Dauphi-
ny, by Mr. Montigny, in the year 1768,
which contained mercury, fulphur, arfenic,
cobalt, iron, and filver. It is grey, whitifh,
and friable. He found it to contain one
pound of mercury, and three or four ounces
of filver per quintal.

After this fhort account of the proper-
ties of the metal, the different dates in which
mercury is found in the earth, may be re-
duced to the following varieties.

STATE

MERCURY. IO3

STATE I.

Native Mercury.

DifTeminated in Earths and Stones, and
moii commonly in its own Ores.

STATE II.
Native Calx of Mercury.

STATE III.
Native Vitriol, and Muriate of Mercury.

STATE IV.
Mercury mineralized by Sulphur; Cinnabar. *

Varieties.

i. Tranfparent cinnabar, red and cryftal-
lized in very fhort triangular prifms, termi-
nated by triangular pyramids.

2. Tranfparent red cinnabar, in octahe-
dral cryftals, confifting of two triangular
pyramids, united at their bafes, and trun-
cated.

G 4 3. Solid

104 MERCURY.

3. Solid compaft cinnabar, of a brown or
bright red > it is fometimes foliated.

4. Red jcinnabar diftributed in ftriae, on a
ftony matrix, or on folid cinnabar ; it is
fometimes compofed of needles like cobalt.

5. Cinnabar in flowers; native vermil-
lion. It is a cinnabar of a brilliant red, of
a fattin appearance, which adheres to dif-
ferent matrices, under the form of a very
fine powder -, it is fometimes cryftallized in
very fmall needles, and then greatly refembles.
the foregoing variety.

STATE V.

Mercury combined with Sulphur and
Copper; black and vitreous Ore of Mer-
cury of Croniledt.

STATE VI.

Mercury united to Sulphur, Arfenic, Co-
balt, Iron and Silver.

STATE VII.

Mercury united to Silver, Native Amalgama
of Silver.

An ore of mercury is known by pound-
ing and mixing it with lime, or alkalies ;
this being thrown on a hot brick, and the

whole

MERCURY. IO$

whole covered with a veflel in the form of a
bell, the mercury is reduced into vapours,
and condenfes on the fides of the veffel. If
the objeft be to difcovcr the quantity of
mercury it contains, the ore, after being
pulverized and wafhed, muft be diililled with
fuch additional matters as are capable of
feizing the fulphur, and difengaging the
mercury. Water is placed in the receiver,
for the purpofe of condeniing and collect-
ing the mercury. If the ore be carefully
weighed before the affay, and likewife the
mercury obtained by diiHllation, the pro-
portional quantity, which may be expected
from any other mafs of the ore, will be
known.

Virgin mercury is eafily feparated, by
pulverizing the ftones in which it is mixed,
and wafhing them in water. The metal
precipitates, and the earth is carried off by
the water. The oresjtof Idria, in Friuli,
are treated in this manner.
, Cinnabar is too volatile to admit of its
fulphur being diffipated by roafting ; but
being almoft always found mixed with a
calcareous or martial fubftance, it may in
general be decompofed by fire, without any
other medium.

Mr. De Jufiieu, in the Memoirs of the
Royal Academy, for the year 1779, has de-
fcribed the procefs made ufe of at Almaden,
in Spain, to obtain mercury from cinnabar.

ThQ

IC6 MERCURY.

The ore containing iron, and a fmall quan-
tity of calcareous ftone, is put into furnaces,
which are formed like reverberatory fur-
naces, and are heated by a fire made on a
grate below. The furnace has no opening,
except eight holes at its back part. At
each of thefe a row of aludels is adapted,
the laft of which refts on a fmall ftruc-
ture, at a confiderable diftance from the
furnace. Between the furnace and the ftruc-
ture at which the aludels terminate, is a
fmall terrace or Hoping bank, the higher
part of which is even with the apertures of
the furnace, and the lower with that of the
fupport of the laft aludel. It is confequently
an inclined plane, and ferves to fupport the
intermediate veflels. If any mercury efcapes
for want of a proper clofure, it is collected
at the junction of the inclined planes of
the terrace. When the fire is applied to the
cinnabar, the iron and calcareous ftone unite
with the fulphur; and the mercury being
reduced into vapours, pafles into the aludels.
After the diftillation, all the aludels are car-
ried into a fquare chamber, whofe floor
Hopes towards a cavity in the middle, into
which mercury is emptied.

Mr. De Juffieu obferves, that the ores of
cinnabar do not emit any exhalation noxious
to vegetables, and that the environs of the
mines of Almida, as well as the ground above
them, are very fertile. He likewife remarked,

that

MERCURY. I07

that the working of this mine is not perni-
cious to the workmen, as has been fuppofed;
and that thole who work in the interior
part of the mine, as felons, are the only
perfons who are fubjecr. to any danger ;
becaufe the fires which they are obliged to
make, volatilize a portion of the mercury,
to the vapours of which they are continually
expo fed.

Mr. Sage, in the Memoirs of the Aca-
demy for the year 1776, has defcribed the
procefs employed to extradt mercury from
cirrnabar, in the Palatinate. The furnace
has a gallery charged with 48 retorts of
caft iron, one inch thick, and three feet
nine inches long, containing about fixty
pounds of the matter to be diiiilled. Thefe
retorts are immoveably fixed in the furnace.
A mixture of three parts of the ore well
pounded, with one part of flaked lime, is
introduced by iron ladles. The heat is pro-
duced by pit coal put in at the two extre-
mities of the furnace, the fides being pierced
in feveral places, to give furncient air to
maintain the combuftion. The mercury
rifes by means of the re-action of the lime
on the fulphur, and is colle&ed in receivers
of earth, adapted to the retorts and one third
filled with water. This operation lalts ten
or eleven hours.

Mercury obtained, or revivified, from cin-
nabar, is very pure, and contains no foreign

matter.

I08 MERCURY.

matter. The mercury met with in com-
merce, is feldom of this degree of purity,
as it is almoft always mixed with foreign
metallic matters, whence it appears tarnifh-
ed, and inftead of dividing itfelf into neat
globules, it flattens, and draws a tail.

Mercury does not appear to be altered by
the action of light. It is very quickly, and
regularly heated ; that is to fay, its dilatation
is extremely regular, as Meffrs. Bucquet and
Lavoifier have (hewn, by their experiments
into the effects of heat on different fluids,
read at the Academy of Sciences. This
phenomenon proves, that mercury is the
fitteft fluid to afcertain exactly the degrees
of heat, and forms the bed thermometers.*

This metallic fluid, expofed to heat in
clofed veffels, boils in the fame manner as
liquids ; a property not peculiar to mer-
cury, but common to filver, gold, and
moft other metals. It is true, that as mer-
cury is more fuiible than any other metal,
it boils fooner, and long before the red
heat. Ebullition is nothing but the tranfi-
tion from the liquid to the vaporous ftate.
The vapour of mercury, which is diftinctly
vifible, in the form of a white fume, and,
for the time, deprives the veilels in which
it is received of their tranfparency, is con-

* De Luc afcertained this point in his Recherches fur les
Modifications de l'Atm&fphere. T.

denfed

MERCURY. IC9

denied by cold into drops of mercury, which
are equal to the quantity put into the retort,
and have fuffered no alteration, provided the
mercury be extremely pure, and the diftilla-
tion carefully conducted. Mercury is there-
fore a very volatile fubftance, which may
be diftilled like water, and in this property
it approaches to the nature of femi-metals.

Boerhaave diftilled the fame quantity of
mercury five hundred times fuccefiively, and
found it not in any refpedt altered. It only
appeared rather more brilliant, heavy, and
fluid ; doubtlefs becaufe the purification
was very accurate. In this diftillation he
obtained a fmall quantity of grey powder,
which confifted of mercury in a Hate of
extreme divifion, and became fluid and
brilliant by Ample trituration in a mortar.
It was an Ethiops per fe.

Diftillation is the beft method of purify-
ing mercury, and of feparating the mixed
metals, with which it is ufually vitiated in
commerce. The foreign metal is found in
the retort, in a brilliant crufl in fome parts,
and blackifh in others. By weighing this
refidue, the quantity of matter, with which
the mercury was vitiated, is known.

The extreme weight of mercury caufed
chemifts to imagine, that it contains the
pure terreftrial principle, or verifiable earth,
in great abundance; but this principle,
when it abounds in bodies, gives them Vo-

lidity;

110 MERCURY*

lidity; and mercury is, on the contrary, very
fufible ; and again the earthly principle is
fixed, and mercury is exceedingly volatile,
Thefe circumftances appearing contradict-
ory, engaged Beccher to admit in this metallic
fluid, a peculiar earth, which he denominated,
as we have before obferved, mercurial earth,
and attributed to it exceffive weight, toge-
ther with volatility. Mercury was there-
fore, according to this chemift, a compound
of three earths, viz. the verifiable, the in-
flammable, and the mercurial. The exift-
ence of the latter having never yet been
proved, this opinion muft therefore be
confidered as a mere unfupported after-
tion. Mercury appears like all metallic
fubftances, to be a peculiar combufti-
ble body, whofe firfl principles have not
yet been feparated. As to the verifiable
earth, whofe properties we have examined
at the commencement of this work, we do
not think that there is reafon to admit it
in mercury, more than in other metals, fince
no fuch principle has been extracted from it.
The fubftance diftinguifhed by that name
by Beccher and Stahl, and fuppofed to
exift in mercury, and in other metallic fub-
ftances, is far from being a fimple and ear-
thy fubftance ; as we have already obferved
in fpeaking of metallic calces in general.

Mercury, reduced into vapour, has a very
confiderable force of expansion, and is ca-
pable

MERCURY. Ill

pable of producing dangerous explofions,
when confined. Hellot related to the Aca-
demy, that a certain perfon, being defirous
of fixing mercury, had put a quantity into
an iron ball, well foldered together. The
ball being thrown into the middle of a heat-
ed furnace, had fcarcely become red, when
the mercury burft through its confinement
with a confiderable noife, and efcaped. Mr.
Baume, in his experimental chemiftry, re-
lates a fimilar fatt, of which GeorTroy, the
apothecary, was witnefs.

Mercury when heated with accefs of air,
changes at the end of fome months into a bril-
liant red powder, of an earthy appearance,
difpofed in fmall fcales. This powder, which
no longer pofieffes the metallic afpeCt, is a
true mercurial calx. The alchemifts, who
believed that the mercury was fixed in this
experiment, called it, improperly, mercury
precipitated by itfelf, or precipitate per fe.
As mercury, though very volatile, requires
nevertheleis the concourfe of air to calcine
it ; an inftrument furliciently commodious
has been invented for this operation, ufually
called Boyle's hell. It is a large glafs vef-
fel, flat at the bottom, fo that the mercury
inclofed within it, forms a very thin ftra-
tum, and confequently prefents a large fur-
face. It is clofed by a ftopper, accurately
fitted to its neck, and perforated by an ex-
ceedingly fmall hole. The veiTel is placed

on

112 MERCURY.

on a fand- bath, and the mercury heated
till it boils. The opening in the (topper,
on account of its minutenefs, fuffers the
air to have accefs to the bottle, without fuf-
fering the mercury to efcape. At the end of
feveral months of digeftion, a calx which is
formed on the furface of the mercury may be
feparated. This is done by pouring the
whole into a piece of clofe linen ; the mer-
cury paffes through by preffure, and the red
calx remains on the cloth. This procefs
may be performed with equal fuccefs, with
a flat bottomed matrafs, into which a fuf-
ficient quantity of mercury is. poured, to
form a thin ftratum. The neck of the ma-
trafs is afterwards drawn out into a ca-
pillary tube, and the point broken off. This
method, contrived by Mr. Baume, is better
adapted to the calcination of mercury, be-
caufe the vefTel contains more air. It is
likewife more eafily heated, lefs expenfive,
and lefs fubjecl to be broken, than Boyle's
vefTel. To fucceed in this experiment,
the mercury muff, be kept in a heat fufficient
to make it boil gently night and day, for
feveral months. By placing a number of
fuch veffels on the fame fand bath, a very
large quantity of precipitate per fe may be
obtained, and a certain quantity may be had
in fifteen or twenty days.

The precipitate per fe is a true calx of
mercury, or combination of that metallic

fubftance,

MERCURY. II3

fubftance^with the bafe of vital air, which
it gradually feizes from the atmofphere.
This is proved in a convincing manner,
from the following circumftances : Firft,
mercury can never be converted into preci-
pitate per fe, without contact of air. Second-
ly, this combination cannot be made, but
with pure air, and does not take place in
the different gales which are not pure air.
Thirdly, the mercury in this experiment be-
comes heavier. Fourthly, when heated in
doled \eilrls, it may be intirely reduced
into running mercury, at the fame time
that a large quantity of elaftic fluid is dif-
engaged, in which ccmbuftible bodies burn
four times more rapidly than in the air of
the atmofphere. This is the fame fluid that
was firlt di (covered by Dr. Prieftley, and by
him called dephlogiiticated air. The mer-
cury lofes by reduction the weight it had
acquired during calcination.

This laft fad:, together with the phenome-
non of calcination, as far as relates to the ne-
celTity of the free admifficn of air, and its di-
minution in the operation, has induced Mr.
Lavoifier to conclude, from analogy as well
founded as any admitted in natural philo-
sophy, that metallic calces are mere com-
binations of metals with the bafe of air. As
the precipitate per fe may be very well
analyfed by heat, and as it feparates into
two principles, pure or vital air, and run-
Vol. III. H ning

114 MERCURY,

ning mercury, it is evident how ftrongly this
valuable experiment tends to explain, and
to prove the pneumatic theory. It is ea-
fily understood, that the bafe of vital air,, or
the oxigynous principle of Mr. Lavoifier,
which was fixed in the mercury, becomes
difengaged by recovering its elafticity with
the affiftance of heat. To reduce precipi-
tate perfe in this manner, it muft be heated
in veflels accurately clofed. If the air has
accefs to it, it remains in the ftate of calx,
becaufe it always finds in the atmofphere
the body which alone has the property of
calcining it. From this circumftance it
was that Mr. Baume infifted, that precipi-
tate per fe is not reducible, but on the con-
trary, fublimes in reddifh cryftals, of a ruby
colour -9 while Mr. Cadet has maintained,
that all precipitates per fe are equally redu-
cible into fluid mercury. Macquer has
{hewn, by an ingenious explanation, which
perfectly agrees with the fadts, that both
thefe chemifts were in the right ; and that
if the calx of mercury be heated with ac-
cefs of air, it fublimes totally, and may
even be melted into a moft beautiful red
glafs, as Mr. Keir, a learned Scotch che-
miit has aflerted, in his tranflation of the
Diftionaryof Chemiftry; but that the fame
calx, though capable of fubliming with the
contaft of air, is reduced into a running mer-
cury, and gives out vital air, when it is
ftrongly heated in well-clofed veflels.

Mercury

mercury. 115

Mercury is not altered by expofure to air.
It is only obferved, that it becomes tarnifh-
ed by the particles of duft, which the air
depofits, and from that circumftance mer-
cury has been called the loadftone of duft.
All bodies, however, feem to have this pro-
perty, though it is moft fenfible in this
metal, on account of its brilliant furface.
But it is not at all changed by this circum-
ftance; nothing more being neceflary to
give it its original brilliancy, than filtra-
tion through a piece of fliammoy leather.

Mercury does not feem to diflblve in
Jwater. Fhyficians are, neverthelefs, in the
habit of caufing a bag full of this metal to
be fufpended in vermifuge decoftions during
their ebullition ; and experience has fhewn,
that this practice is attended with good
effe&s. Lemery affirms, that mercury lofes
part of its weight by this decoftion. It
is probable, that a principle, fimilar to that
of fmell, emanates from the mercury; a
principle fo fugitive and fubtle, that its
weight cannot be found. It is perhaps this
principle that communicates the anthelmin-
tic virtue to water*

Mercury does not unite to earths more
than other metallic fubftances; its red calx
or precipitate per fe might perhaps fix in
glafles, and colour them, as is obferved to
happen with the calx of arfenic.

The adtion of barytes, magnefia, lime,
and alkalis on mercury, are not known.

H 2 The

1 16 MERCURY.

The vitriolic acid does not ad: on this
metallic fubftance, but when it is well con-
centrated. To make this folution, one part
of mercury is poured into a glafs retort,
and one part and a half, or two parts of
oil of vitriol are added ; the mixture is
heated, and a violent effervefcence is foon
after excited ; the furface of the mercury
becomes white, and a powder of the fame
colour is feparated, which renders the acid
opakej and a large quantity of fulphureous
gas is difengaged, which may be collected
over mercury. This method, as we have
feen in fpeaking of the vitriolic acid, i§
moil commonly ufed to obtain that gas.
A portion of water charged with fulphu-
reous gas, and in the ftate of volatile ful-
phureous fpirit, likewife paifes over. When
this diftillation is urged, till the fulphu-
reous acid no longer paries over, a white
opake very cauflic mafs is formed at the
bottom of the retort, which weighs one
third more than the mercury made ufe of,
and ftrongly attracts the humidity of the
air. The greateft part of this mafs is a
calx of mercury united to a fmall portion
of the vitriolic acid. It is confiderably
fixed, according to the obfervations of
Kunckel, Macquer, and Bucquet. In this
operation the oil of vitriol is decompofed
by a double elective attraction; the mer-
cury.

MERCURY. II7

cury, which is a combuftible fubftance,
unites to the oxigynous principle contained
in the acid, while the heat difengages the
fulphureous gas and the water. The metal
muft therefore be in the ftate of a calx,
and muft confequently have much more
fixity than fluid mercury.

A portion of this vitriolic mercurial mafs
is foluble in water. When a large quantity
of water is poured upon it, it mixes with the
mafs, and a white powder precipitates, if
the water be cold ; but if boiling water be
ufed, the powder is of a beautiful brilliant
yellow colour, which is fo much the more
lively, as the quantity of water and the
heat are greater. This was anciently called
turbith mineral, or yellow precipitate. The
water which ferved to warn it is decanted,
and a new quantity of boiling water is pour-
ed on the turbith, in confequence of which
it becomes of a ftill more lively yellow.
The warning is repeated a third time, to
deprive it of all the vitriolic acid it con-
tains. In this ftate it has no longer any tafte,
but is a mercurial calx, which when urged
by fire in a retort, becomes firft of a deeper
colour, and is then reduced into running
mercury, giving out a great quantity of vital
air. Kunckel mentions this experiment,
and it has been fuccefsfully repeated by
Meffrs. Monnet, Bucquet, and Lavoifier,
who have made it in the moft accurate

H 3 manner.

1 1 8 MERCURY.

manner. I have alfo repeated it many times
with fuccefs. It proves, as we have ob-
ferved, that the vitriolic acid is formed of
fulphur, the oxigynous principle, and wa-
ter ; but a very violent fire is neceffary to
effect the reduction. It is perhaps for want
of a fufficient heat, that Baume did not
obtain mercury ; and that he affirms, that
it cannot be reduced to its metallic form,
but by the addition of a phlogiftic or com-
buftible matter. The vitriolic mercuriate
being kept heated in the fame retort in
which it has been diffolved without unlut-
ing, or wa(hing the mafs to deprive it of
the portion of acid, the decompofition ne-
verthelefs takes place, and it is reduced
into running mercury, in proportion as the
oxigynous principle, which it had taken
from the vitriolic acid, becomes elaftic,
and confequently is converted into vital air
by the combination of heat, according to
the modern chemifts.

The water which has been poured on the
white vitriolic mercurial mafs, is loaded with
a portion of the acid which was not decom-
pofed 'y but as calx of mercury is very foluble
in that acid, a certain quantity is always taken
up, fo that the water holds in folution a
true vitriol of mercury. By evaporating
moft of the water, this fait is depofited in
fmall needles, the form of which has not
t>een determined, becaufe they are fcarcely

confiftent,

MERCURY. 119

confident, and quickly attradt humidity.
When boiling water is thrown on the cryftals
of the vitriol of mercury, they become yel-
low, and in the ftate of turbith mineral, be-
caufe the water feparates the acid, which ad-
heres but weakly, and leaves the calx pure.
The fame event happens, when the water em-
ployed for the firft wafhing of the mercurial
mafs is moftly evaporated, and the remain-
der afterwards diluted by the fudden addi-
tion of a large quantity of boiling water,
inftead of bringing it to cryftals. If cold
water be ufed, the precipitate is white ; but
it immediately aftumes a yellow colour by
the addition of boiling water. In this man-
ner the folution of the calx of mercury may
be rendered decompofable, or not, by water.
For this purpofe it is fufficient to evaporate
it nearly to cryftallization, or to charge the
acid with all the calx it is capable of dif-
folving ; for then the union of thefe two
bodies is eafily deftroyed by water. If a
fmall quantity of acid be added, water is
no longer capable of caufing a precipitation.
I obferved this in the mod fatisfa&ory man-
ner, by diflblving well wafhed turbith mi-
neral in weak fpirit of vitriol ; the folution
is not faturated with mercury, and is at the
fame time not precipitable by water. But
if the folution be charged with as much
turbith mineral as it can diflblve by the
afliftance of heat, which may be done by

H 4 adding

120 MERCURY.

adding that fubftance till it is no longer
taken up ; then the lblution being poured
into cold water, affords a white precipitate ;
or if into hot water, a yellow powder. In
this ftate, if a fmall quantity of fpirit of
vitriol be added, it ceafes to afford any pre-
cipitate. The white calx which the vitriol
of mercury depofits, when cold water is
poured on it, is very foluble, and may be
made to difappear, by adding fpirit of vi-
triol to the mixture.

Vitriol of mercury may be decompofed
by magnefia and lime, a yellow precipi-
tate being depolited ; and fixed alkalies fe-
parate a calx of mercury nearly of the fame
colour. The cauflic volatile alkali precipi-
tates it, but very fparingly and flowly. It
muff be obferved, that thefe precipitates of
mercury are varioufly coloured, according
to the ftate of the folution, and the nature
of the precipitating fubftance, and their
quantities likewife differ. They are very
abundant when the folution is highly charg-
ed 'y and if, on the contrary, a folution which
is not faturated with mercury, be -decom-
pofed, every portion of calx, which is fepa-
rated by the firft drcps of the precipitate,
is re-diffolved by the excefs of acid. But
when that excefs is faturated, the precipi-
tate becomes permanent. Hence it appears,
that alkalies act on the acid combined with
the mercury, more rapidly than on the acid

at

MERCURY. 121

at liberty. Thefe different calces of mer-
cury, precipitated by alkaline fubftances,
are reducible in clofe veffels, without addi-
tion. To obtain them pu^e, it is neceffary
that they mould be ievcral times warned
with diftilled water.

The nitrous acid is decompofed by mer-
cury with the greateft rapidity. The folu-
tion is effected without the application of
external heat, and with various degrees of
activity, according to the fiate of the acid.
The common aqua fortis of the mops, acts
on mercury without emitting any confider-
able quantity of red vapours. If a fmall
quantity of fuming fpirit of nitre be added,
or if the mixture be heated, the combina-
tion proceeds much more rapidly, and a
very large quantity of nitrous gas is difen-
gaged. The mercury being reduced to a
calx, remains diffolved. The folution is
green, but it lofes that colour at the end of
a certain time. By this procefs, the acid
takes up a quantity of mercury, equal to its
own weight. Bergman hasobferved, in his
diiTertation on the analyfis of waters, that
nitrous mercurial folutions differ from each
other according to the manner of their pre-
paration ; that which is made in the cold,
and without the difengagement of red va-
pours, not being decompofable by the addi-
tion of diitilled water; but if the folution
be afTiited by heat, and a large quantity of

■ nitrous

122 MERCURY.

nitrous gas be produced, a precipitate will
fall down on the addition of water. Such
a folution cannot with certainty be made
ufe of in the analyfis of mineral waters, as
we fhall hereafter obferve. This phenome-
non is, I apprehend, owing to the fame
caufe in the nitrous, as in the vitriolic, folu-
tion. Pure nitrous acid, affifted by heat, is
capable of fuperfaturating itfelf with calx of
mercury, and holding it fufpended. This
kind of folution with excefs of mercury,
will be precipitated by diftilled water, which
changes the denfity of the liquor, and di-
minifhes its adhefion to the mercurial ni-
tre ; the precipitate therefore is a true tur-
bith ; which is very yellow, if warm water
be poured on the fuperfaturated folution,
but is merely white if cold water be ufed.
The yellow colour may however be inftant^
ly communicated by waihing in warm wa-
ter. But, on the other hand, as the folu-
tion made in the cold, contains only mer-
curial nitre, without an excefs of calx, dif-
tilled water occafions no precipitate. I think
myfelf juftified in accounting for the fadls
in this way, from a circumftance which I
have obferved a great number of times, viz.
that the fame mercurial nitrous folution
may be rendered decompofable or not by
water, accordingly as mercury or acid are
added, and this may be repeated many times.
For this purpofe, mercury is to be diflblved

without

MERCURY. 123

without heat in the nitrous acid, in as large
a quantity as can be taken up; this folution
is not decompofable by water, though ni-
trous gas has efcaped : but if mercury be
added to this by the afliftance of heat, it be-
comes capable of affording a precipitate with
water. By the fame theory it is very evi-
dent, that a nitrous folution, which does not
afford a precipitate by the addition of water,
may acquire that property by fimple heat-
ing. The heat, in fad:, difengages nitrous
gas, and this difengagement cannot be made
without the deftru&ion of a certain quan-
tity of the acid. The proportion of mer-
curial calx to the remaining acid, becomes
of courfe greater, and the excefs is no longer
combined, but adheres to the mercurial
nitre, and is fufpended in fuch a manner,
that water can precipitate it eafily. I have
afcertained the faft, that mercurial folutions
afforded only the excefs of calx, by the ad-
dition of water, and do flill retain a portion
of true mercurial nitre, which may be de-
compofed by alkalies ; in the fame manner
as happens with the mercurial vitriolic mafs,
warned for the preparation of turbith mine-
ral. This portion of mercurial nitre may
even be brought to cryftallize.

The folution of mercury in the nitrous
acid, is exceedingly cauftic, and capable of
corroding and deftroying our organs. When
it falls on the fkin, it forms fpotS of fo deep

a purple,

124 MERCURY.

a purple, that they appear black ; thefe fpots
cannot be diffipated, but by the feparation
of the epidermis, which fcales off. The
folution is ufed .as a powerful efcharotic in
furgery, by the name of mercurial water.

The folution of mercury in the nitrous
acid, is capable of affording cryftals, which
differ from each other in their form, accord-
ing to the ftate of the folution, and the cir-
cumflances accompanying the cryftalliza-
tion. Thefe varieties being carefully ob-
ferved, appear to confift of four diftinit fpe-
cies, which I (hall here defcribe.

i. A folution made in the cold, affords,
by fpontaneous evaporation, after feveral
months, very regular cryftals. Mr. Rome
de Lifle has defcribed them accurately.
They are flat folids, of fourteen faces, form-
ed by the union of two tetrahedral pyramid?,
truncated very near their bafe, and likewife
at the four angles, which refult from the
junction of the pyramids.

2. If the fame folution made in the cold
be evaporated and left to cool, it depofits in
the courfe of 24 hours, a kind of very acute
prifms ftriated obliquely acrofs their length,
which are formed by the fucceffive applica-
tion of fmall laminae, placed flopewife upon
each other, like tiles, (botanifts denote this
by the term imbricatim). On a near exami-
nation of the elements of thefe prifms, I
found that the laminae which compofe them,

are

MERCURY. 125

are folids, with fourteen facets, fimilar to
the cryftals obtained by fpontaneous evapo-
ration, but imaller, and more irregular.

3. If a nitrous folution be made by a
mild and regulated heat, it affords, by cool-
ing, cryftals, in flat, very long, and very a-
cute needles, ftriated lengthwife; thefe are
the moft commonly obtained, and have been
defcribed by the greateft number of che-
mifts, efpecially by Macquer, Rouelle,
Baume, &c.

4. Laftly, If this folution be more heat-
ed, fo as to become decompofable by wa-
ter, it ufually takes the form of a white #
and irregularly formed mafs, fimilar to the
vitriolic combination. In this circumftance

I have fometimes had a confufed aggregate
of fmall very long needles, of the appear-
ance of fattin, and flexible, which followed
the motion of the liquor. They were per-
fectly fimilar to the brilliant and filver co-
loured dendrites, which I have often ob-
f^ved on the fides of bottles, containing
terra foliata tartari. It is proper to add,
that this laft folution, which affords only-
irregular and confufed cryftals, or fhapelefs
maffes, becaufe it contains much fuper-
abundant calx of mercury, may be rendered
capable of a more regular cryftallization by
the addition of acid.

Thefe feveral mercurial nitres prefent
nearly the fame phenomena. They are very

cauftic,

126 MERCURY.

cauftic, and corrode the fkin in the fame
manner as their folutions ; they detonate on
burning coals. It muft be obferved with
regard to this property, that it is much more
fenfible in the very regular cryftals of four-
teen facets, than in thofe which have the
form of fmall needles; and that it does not
exift at all in the white mafs precipitated
from the ftrongly heated folution. The de-
tonation of mercurial nitre is fcarcely per-
ceptible in cryftals newly formed, but is
rendered fufficiently fenfible by fuffering
them to dry for fome time on blotting
paper. If they be then placed on an ig-
nited coal, they melt, become black, and
extinguish the place on which they are put ;
but their borders, which become dry, throw
out fmall reddifh fparks, with a noife fimi-
lar to that of a flight decrepitation. When
the very dry cryftals are ufed, a ftronger
whitifh flame efcapes, which foon ceafes.

Mercurial nitre melts when heated in a
crucible, and emits very thick red vapours.
In proportion as it lofes its water and ni-
trous gas, it takes a deeper yellow colour,
which is afterwards converted to an orange,
and laftly to a brilliant red. In this ftate it
is called red precipitate. If this prepara-
tion is intended to be employed in furgery
as a cauftic, it muft be made in a matrafs
by a mild heat, in order that it may retain
a portion of the acid, to which it owes

its

MERCURY. I27

its corrofive power. Nothing remains af-
ter it has been ftrongly heated, but a calx
of mercury, formed by the union of the me-
tal to the oxigynous principle of the nitrous
acid. Mercurial nitre diftilled in a retort,
affords a fubacid phlegm, and nitrous acid
at firft, after which it becomes red precipi-
tate ; and a ftronger heat being applied, oc-
cafions a large quantity of vital air, with a
fmall portion of mephitis to be difen-
gaged, the mercury being fublimed in the
metallic form. It is from this experiment,
made with the greateft accuracy, that Mr.
Lavoifier has fucceeded in proving the com-
pofition of the nitrous acid, as we have ob-
served in the hiftory of that faline fubftance.
Mercurial nitre becomes yellowifh on ex-
pofure to air, and is very flowly decompofed.
It is foluble in diftilled water, in a larger quan-
tity when boiling than in the cold, and con-
fequently cryftallizes by cooling. When this
fait is diffolved in water, a portion remains,
which is of a yellowifh colour, and is not
taken up. Mr. Monnet calls this matter
nitrous turbith, and obferves, that a large
quantity may be obtained, by waffling a ni-
trous mercurial mafs, evaporated to drynefs,
fuch as is made for the preparation of red
precipitate. If it be intended that the mer-
curial nitre (hall be intirely diffolved, water
muft be employed, in which aqua fortis
muft be poured, until the precipitate dif-

appears.

128 Mercury:.

appears. I have obferved, when boiling
water is poured on the pureft mercurial
nitre, it immediately becomes yellow, and
affords a nitrous turbith, of a deep colour,
which when expofed to fire, becomes red more
quickly than that which is made by the
vitriolic acid. Nitrous turbith is in gene-
ral more accurately calcined, than vitriolic
turbith ; which happens, as we have already
obferved reflecting other combuftible fub-
ftances, from the nitrous acid fuffering its
oxigynOus principle to be difengaged more
eafily ; for which reafon the nitrous acid is
more decompofable than the vitriolic.

Ponderous earth, magnefia, lime, and
alkalies, decompofe mercurial nitre, and
precipitate the metal in the ftate of calx.
Thefe precipitates are of different colours,
weight, and quantity, according to the ftate
of the folution. Cauftic fixed alkalies af-
ford a yellow precipitate, more or lefs brown,
or of a brick colour, according as their cauf-
ticity is more perfecT:. Volatile alkali pre-
cipitates the nitrous mercurial folution, of
a grey flate colour, provided it be of that
kind which water cannot decompofe ; but
the fame fait produces a white precipitate,
in a faturated folution of mercury, fuch as
water can precipitate. Thefe differences
have been accurately obferved by Bergman.
The precipitates are mere calces of mer-
cury, more or lefs remote from the metallic

ftate;

MERCURY. I29-

ftate; they are all reducible without addition,
and by mere heat in clofed veffels, and all
afford pure air during their reduction.
Thofe which have been precipitated by cre-
taceous alkalies, afford a certain quantity of
cretaceous acid by the action of heat. The
precipitates of mercury, formed by alkaline
intermediums, have a property, difcovered
by Mr. Bayen, which muft not be paffed
over in filence. They detonate like gun-
powder, when expofed in an iron fpoon to
a gradual heat, after having been triturated
in the quantity of half a drachm, with fix
grains of flowers of fulphur: after the de-
tonation, a violet powder remains, which
may be fublimed into cinnabar.

The vitriolic acid, and the falts into which
it enters, likewiie decompofe mercurial nitre,
on account of the ilronger affinity of the vi-
triolic acid to mercury. If fpirit of vitriol,
or a folution of the vitriols of vegetable or
mineral alkali, or of any other vitriolic fait,
be poured into a folution of mercurial nitre,
a whitifli precipitate is formed, if the ni-
trous folution be not faturated ; but it is
yellower in proportion as the mercurial
nitre contains lefs acid, and more metal.
This precipitate is either1 vitriol of mercury,
or vitriolic turbith. Mr. Bayen found that
it always retains a portion of nitrous acid.

The muriatic acid has no fenfible adioa

on mercury, though it be one of thofe which

Vol. III. ~ I has

I30 MERCURY.

has the ftrongeft: affinity with that metal ;
but its adtion on mercurial calces, with
which it forms a peculiar neutral fait, is
very powerful. This combination takes
place whenever the marine acid is brought
into contact with the calx, in a ftate of ex-
treme divifion. If a fmall quantity of mu-
riatic acid be poured on a nitrous folution
of mercury, this acid feizes the metal, and
forms a fait which is precipitated in a kind
of whitifh coagulum, called white precipitate;
the marine falts with bafe of alkali, or of any
falino-terreftrial fubftance, abundantly pro-
duce the fame efFeft,. and form belides, ear-
thy neutral falts, differing according to the
nature of the bafe. But it mull be obferv-
ed, with refpeft to this precipitation, that
it does not take place when the aerated, or
dephlogifticated muriatic acid is ufed ; be-
caufe, though this acid takes the calx of
mercury from the nitrous acid, the fait
which it forms with that calx, is very folu-
ble in water; whereas, the fait formed by
the common muriatic acid, is not at all fo-
luble.

This acid has a ftronger affinity than the
vitriolic acid with mercury, and occafions
the fame precipitate in the vitriolic folutions
of that metal, as it does in the nitrous folu-
tions. The compound of muriatic acid, and
mercurial calx, may exift in two ftates, as
we have before obierved, according to the

fimple

MERCURY* Ijl

fimple or aerated ftate of the acid ; the lat-
ter conftitutes corrofive fublimate, and the
former, mercurius dulcis.

There are feveral procefTes for preparing
corrofive fublimate, or corrofive mercurial
muriate : in general, equal parts of dried
mercurial nitre, decrepitated marine fait,
and calcined or white martial vitriol, are
mixed and put into a matrafs, two thirds
of whofe capacity are left empty. This vef-
fel is plunged into a fand bath, and gradual-
ly heated till its bottom becomes of an ob-
fcure red -> the vitriolic acid difengages that
of the marine fait ; the latter feparates the
mercury from the nitrous acid, which af-
fords the oxyginous principle, fo that it be-
comes dephlogifticated muriatic acid ; it
then combines with the mercurial calx, and
forms corrofive mercurial muriate, which
is fublimed in the form of flattened and
pointed cryftals to the upper part of the
matrafs j the nitrous acid being difiipated in
the form of nitrous gas. The reiidue is
reddifh or brown, and contains vitriol of
foda, (formed by the union of the vitriolic
acid with the bafe of the marine fait) and
calx of iron. This fait is prepared in the
large way in Holland, by triturating equal
parts of mercury, marine fait, and vitriol
together, and expofing the mafs to a vio-
lent fire. In this operation the vitriolic
acid, difengaged from the vitriol by heat,
1 2 appears

1J2 lilERCURY.

appears to caufe the muriatic acid to pais into
the dephlogifticated ftate, fince this laft
only is prefent in fufficient quantity perfectly
to diflblve the mercury made ufe of. The
corrofive mercurial muriate, may likewife
be obtained by fublimation, from mixtures
of martial vitriol, marine fait, and mercu-
rial precipitates, by fixed alkalies, or turbith
mineral.

Boulduc has given a very good procefs for
preparing corrofive fublimate -, but Spiel-
man remarks, that it was before defcribed
by Kunckel, in his Chemical Laboratory.
It confifts in heating equal quantities of
vitriol of mercury, and decrepitated marine
fait in a matrafs; the fublimate is volati-
lized, and the refidue confifts of Glauber's
fait. This method affords a very pure cor-
rofive fublimate ; whereas that ufed in com-
merce, and even that prepared in the fmall
way, with martial vitriol, always contains a
fmall quantity of iron. It is likewife more
eafy to execute, and more economical. We
muft here obferve, that this operation proves
that the vitriolic acid has the property of
dephlogifticating the muriatic acid. Mr.
Monnet affirms, that he has likewife ob-
tained this fait, by treating, in a retort, very
dry fea fait and mercury precipitated from
its nitrous fdlution by fixed alkali. In all
thefe preparations of corrofive fublimate,
care muft be taken not to break the fubli-

matory

MERCURY. 133

matory veiTel till it is entirely cool, in order to
avoid the vapours of the fublimed fait. Laft-
ly, there is another way of preparing the cor-
rofive mercurial muriate more readily- it
confifts in pouring into a folution of mercu-
rial nitre, a quantity of dephlogiflicated mu-
riatic acid, and evaporating the mixture.
When the nitrous acid is evaporated, the
liquor affords by cooling, cryftals of corro-
five mercurial muriate. There is reafon to
think, that when the dephlogiflicated mu-
riatic acid of Scheele fhall be better known,
the corrofive mercurial muriate of the fhops
will be prepared by this fimple folution.*

Corrofive fublimate, or mercurial muri-
ate, is a neutral faline fubftance, which de-
fences to be carefully attended to by che-
mifls and phyficians j it pollelTes a great num-
ber of properties which are highly neceiTary
to be known, and of which we fhall pro-
ceed to give a /ketch. Its tafle is exceed-
ingly cauftic; the fmalleft quantity being
laid upon the tongue, leaves for a very long
time an highly difagreeable ftyptic and me-
tallic tafte. This imprelTion is carried even
to the larynx, which it contrails fpafmodi-
cally for a long time, efpecially in delicate
peffons. The action of this fait is ftill
ftronger on the tunics of the ftomach, and
the inteftines. When it is applied to thefe

* See Scheele's E flays.

I 3 for

X34 MERCURY.

for any length of time, it corrodes them,
and deftroys their fubftance, for which rea-
fon it is one of the moft violent poifons we
Jcnow, The caufticity of corroiive fubli-*
mate, appears to depend on the fiate of the
mercury, as Macquer has very ingenioufly
obferved. It cannot be attributed to the
muriatic acid, as fome authors have thought;
for the mercury is more than treble the
quantity of the acid. On this account, the
fait renders fyrup of violets green, rather
than red, according to the obfervation of
Rouelle. The tafte of corrofive fublimate
is befides exceffively ftronger than that of
the muriatic acid, A dram of fpirit of fait,
diluted with water, may be taken with
impunity -y whereas a few grains of corroiive
fublimate, dilTolved in the fame quantity of
water, would poifon without remedy. Buc-
quet thought that this extreme ftrength of
tafte depended on the combination of the
two bodies, and from thence deduced one of
his ftrongeft proofs of the law of affinity,
which eftablirhes, that compounds have new
properties, very different from thofe of
either of their component parts.

Corrofive mercurial muriate is not fenfi-
bly altered by light; heat volatalizes, and
femi-yitrifies it. If it be ftrongly heated
with accefs of air, it is diffipated in the form
pf a white fume, whofe effects on the ani-
mal ceconomy are very a&ive, and exceeding-

MERCURY. I35

ly dangerous. When heated flowly, and by
degrees, it fublimes in a cryftalline and re-
gular form, into prifms, fo flattened, that it
is impoffible to determine the number of
their faces.. They terminate in very acute
fummits, and have been very properly com-
pared to the blades of poignards thrown
confufedly among each other. Fire alone
is not capable of decompofing this fait, nei-
ther is it fufceptible of alteration from the
air. It is foluble in nineteen parts of water,
and cryftallizes by evaporation, in flattened
prifms, very fharp, their extremity being
fimilar to thofe obtained by fublimation.
The fpontaneous evaporation of this folution
has feveral times afforded me oblique an-
gled parallelopioeds, whofe extremities were
truncated flant-wife. Mr. Bucquet obferv-
ed the fame fadt. Mr. Thouvenel has ob-
tained cryftals of this fait, in hexahedral
prifms, a little flattened.

Ponderous earth, magnefia, and lime, de-
compofe the corrofive mercurial muriate,
and precipitate the mercurial calx. The
phagedenic water made ufe of as a corrofive,
by furgeons, is made by throwing half a
dram of corrofive fublimate, in powder, in-
to a pound of lime-water ; a yellow preci-
pitate is formed, which renders the fluid
opake, and it is employed before this fub-
fides. Fixed alkalies precipitate from cor-
rofive fublimate, an orange coloured calx,
I 4 which

I36 MERCURY.

which becomes deeper coloured by keeping.
The volatile alkali affords a white precipi-
tate, which after a fhort time affumes a flate
colour.

Acids and neutral alkaline falts, produce
no change in the corrofive mercurial muri-
ate, but it contracts an intimate union with
fal-ammoniac, without decompofition . This
very lingular faline compound, which was
highly efteemed by the alchymifts, and cal-
led by them fal alembroth, fait of art, or of
wifdom, &c. is formed either by fublima-
tion or cryftallization. The fal-ammoniac
renders the mercurial muriate very foluble,
fince, according to Baume, three ounces of
water charged with nine drachms offal-am-
moniac, diflblves five ounces of fublimate.
This folution is made with heat, and af-
fords a folid mafs in cooling. A prepara-
tion, called white mercurial precipitate, is
made from this fait. A pound of corrofive
mercurial muriate in powder, is thrown into
a folution of the fame quantity of fal-am-
moniac 1 when the fait is perfectly difibl-
ved, a folution of cretaceous vegetable alka-
li is added, which forms a white precipi-
tate, which is wafhed and dried in the form
of fmall lozenges. In this operation the
fixed alkali difengages the volatile alkali of
the fal-ammoniac, which precipitates the
mercury in a white calx. Heat, and even
light, give this precipitate a yellow colour,

Corrofive

MERCURY. I37

Corrofive mercurial muriate is altered by
inflammable gas. Sulphur does not change
it, but liver of fulphur decompofes this, as
well as all the other folutions of mercury ;
a black precipitate being produced, which
arifes from the combination of the fulphur
with the mercury. Mofl of the femi-me-
tals we have examined, are capable of de-
compoiing this fait, and each decompofition
exhibits peculiar phenomena, which well
deferve to be examined.

If two parts of corrofive fublimate, with
one of regulus of arfenic, be diitllled by a
mild heat, a tranfparent fubilance, of the
confidence of oil, paffes into the receiver,
part of which foon cendenfes into a kind of
white jelly, called corrofive oil, or butter
of arfenic. If the heat be continued after
the butter has paiTea over, running mercury
is obtained : fo that the procefs affords a
method of determining accurately the prin-
ciples of corrofive mercurial muriate. The
butter of arfenic does not appear capable of
cryftallization, melts with gentle heat, and
is fo cauftic, that it inltantly deftroys the
organs of animals. It is foluble in water,
which partly decompofes it ; but its other
properties are unknown. Calx of arfenic
does not afford it.

The effecls of cobalt, nickel, and manga-
nefe, on corrofive fublimate, have not been
examined. Bifmuth, regulus of antimony,

and

I3S MERCURY.

and zink, decompofe this laft fait with great
facility. When two parts of corrofive mer-
curial muriate, and one part of bifmuth, are
diftilled together, a thick fluid fubftance is
obtained, which congeals into a mafs of a
greafy appearance, fufible by heat, and pre-
cipitable by wafhing with much water ; and
in a word, a true butter of bifmuth. Poli,
who firft defcribed this experiment, in the
Hi (lory of the Royal Academy for the year
1713, affirms, that when this butter is fub-
limed feveral times, there remains in the
veffel, a powder of the colour of oriental
pearls, very foft to the touch, and as it were
glutinous ; he propofes this powder to be
employed as a pigment.

If two pounds of regulus of antimony,
and two pounds of corrofive mercurial muri-
ate be accurately mixed together, heat is
excited, which (hews that there is a rapid
action between them. If the mixture be
diftilled by a gentle heat, a thick liquor is
obtained, which becomes fixed in the recei-
ver, and often in the neck of the retort, in
the form of a white mafs, called butter of
antimony. This butter ufually weighs fix-
teen ounces and a few drachms. The refi-
.dueis compofed of mercury, and a grey
powder of regulus of antimony, which floats
on the metallic fluid. If the diitillation be
continued after the butter of antimony has
pafled over, a new receiver being adapted,

running

MERCURY. 139

running mercury is obtained, foiled by a
fmall quantity of the butter of antimony,
which it is impoflible intirely to clear out
of the neck of the retort. Mr. Baume, who
has accurately defcribed this operation, af-
firms, that by this procefs, twenty two oun-
ces of running mercury may be obtained,
one ounce of regulus in powder, mixed with
the mercury, and fix drachms twenty-four
grains of regulus melted in the retort.
The latter is partly calcined into red and
filver coloured flowers. In this experiment
the regulus of antimony is calcined by the
oxyginous principle, which is feparated from
the calx of mercury, and unites to the mu-
riatic acid, with which it forms the butter
of antimony. The fame decompofition
takes place equally well with crude anti-
mony; one part of that mineral in powder
being diftilled with two parts of corrofive
mercurial muriate, affording a butter of an-
timony. But the reiidue, inftead of con-
taining running mercury, exhibits a combi-
nation of fulphur with that femi-metal.
This combination may be fublimed by a
ftronger fire, into red needles, improperly
called cinnabar of antimony.

The butter of antimony may be prepared
by feveral other methods. Jt i?'bbtained in
all cafes, where the regulus in vapour meets
the marine acid in the ftate of gas ; but the
decompofition of corrofive fublimate is the

procefs

I40 MERCURY.

procefs which affords it with the greateft
facility, and in the greateft plenty. This
compound is in a folid form ; it cryftallizes
in thick parallelopipeds ; its caufticity is
Sufficiently ftrong to deftroy both animal
and vegetable matters in a very fhort time.
The action of light changes it : by a low
heat it is melted, and becomes fixed by cool-
ing. It is eafily deprived of its white. co-
lour.; and it may be rectified by diftillation.
When expofed to the air it attracts moifture,
and is diffblved into a thick fluid, apparently
oleaginous : it does not completely di-flblve
in water, the greater part being decompofed
by that fluid. When butter of antimony
is thrown into diftilled water, a very abun-
dant precipitate is immediately formed,
which is known by the name of emetic
powder, or powder of Algaroth, from the
name of an Italian phyfician who firft ufed
it. It has been improperly called mercurius
vita?. This precipitate is a calx of anti-
.mony, which is violently purgative and
emetic in a fmali dofe, as for example, three
or four grains. In order to obtain it very
pure, it muft be warned feveral fucceffive
times in diftilled water. Its properties are
different from the other calces of this femi-
metal, whi£h have not fo ftrong an action
on the animal ceconomy. A portion of this
calx remains diffblved in the water ufed in
warning the butter of antimony, in which

it

MERCURY. 141

it is fufpended by the acid taken up by that
fluid. This facl may be afcertained by the
addition of a fmall quantity of alkali, which
occafions an abundant white precipitate. It
is therefore the excefs of calx with which
butter of antimony is charged, that gives it
the property of being decompofed by water,
as well as that of taking the form of a folid
mafs. Butter of antimony diffblves with
heat and effervefcence in the nitrous acid ;
a large quantity of nitrous gas being at the
fame time difengaged with conliderable agi-
tation of the fluid. The butter of antimony
difappears, and the liquid becomes of a yel-
low reddifh colour. It is a folution of calx*
of antimony in aqua regia. The calx is
foon depofited in the form of a powder, or
white magma. If the folution of butter of
antimony by the nitrous acid be evaporated
to drynefs immediately after it is made,
a very white calx is obtained. This calx is
diluted with its own weight of the fame
acid, which is likewife evaporated, and the
fame procefs is a third time repeated ; after
which the matter is calcined in a crucible
kept red hot for about half an hour, and
affords a calx, which when cold, is found to
be white on the upper part, and of a role
colour below. Thefe two portions mixed
together, constitute the preparation called Be-
zoar mineral. Macquer conliders it as a per-
fect calx of regulus of antimony, and thinks it

abfolutely

142 MERCURY-

abfolutely fimilar to diaphoretic antimony.
But Lemery, who has carefully defcribed
this preparation, recommends, that it fhould
be calcined till it has but a very flight de-
gree of acidity; his intention therefore is,
that it fliould retain a certain quantity of
acid, which muft neceflarily make a differ-
ence between this precipitate and calx of
antimony.

Corrofive mercurial muriate is decompo-
fed by zink, as Pott informs us, and as I
have myfelf many times experienced. If a
mixture of two parts of this fait, with one
part of zink in filings, or coarfe powder,
be diftilled in a glafs retort, a very v/hite
and folid butter rifes, which cryftallizes in
fmall united needles, fimilar to the aggre-
gates of which ftala&ites are compofed.
The mercury remains pure in the retort, and
paffes over after the butter of zink. This
butter fumes flightly when taken* out of the
receiver, and melts with a mild heat, be-
comes coloured by inflammable vapours,
and is partly decompofed by water, like but-
ter of antimony.

The raoft Angular property of corrofivc
mercurial muriate, relative to its alteration
by metallic fubftances, and at the fame
time the moft important of its properties,
is its combination with running mercury.
When faturated with this metallic fluid, it
lofes moft of its properties, especially its

tafte

MERCURY. 143

tafte and folubility. To make this com-
bination, corrofive fublimate was formerly
triturated in a glafs mortar with running
mercury, added by a little at a time, till no
more could be made to difappear. The
quantity of metallic fluid, which the fait
takes up by this procefs, amounts to three-
fourths of its weight, as Lemery and Baume
have obferved. The mixture was placed in
fmall veflels, two thirds of which were left
empty, and in this manner fublimed *hree
times fucceffively ; care being taken each
time to feparate a white powder which is
found beneath the fublimed matter, and is
very corrofive. The product called fweet
fublimate, mercurius dulcis, cr aquilaalba,
or more properly mild mercurial muriate,
differs from corrofive fublimate by its infolu-
bility in water, by its infipidity, and by
its crystalline form. The cryftals obtained
by flow fublimation, are tetrahedral prifms,
terminated by four fided pyramids ; two
very long and tetrahedral pyramids are
frequently united at their bafe, and form a
very acute octahedron.

The procefs we have defcribed for the
preparation of mercurius dulcis, is incon-
venient in many reflects. The trituration
of corrofive fublimate with running mer-
cury, till the latter difappears, is very tedi-
ous and difficult, and at the fame time a
fubtle powder rifes of fo pernicious a qua-
lity,

144 MERCURY*

lity, that the operator is under the neceffity
of covering his mouth and nofe with a
cloth. The mercury is never absolutely
made to difappear in the mortar, and the
fublimations are very flow. Mr. Baume
advifes a fmall quantity of water to be
poured on the matters intended to be tri-
turated ; by this means the operation is
rendered more eafy, and the faline powder is
prevented from rifing. He likewife employs
levigation, by which the extinction of mer-
cury is greatly facilitated. Laftly, in order
to be certain of obtaining mercurius dul-
cis, entirely free from fublimate, Zwelfer,
Cartheufer, and Baume, propofe to pour on
the mild mercurial fublimate, a quantity
of warm water, in order to diflblve the cor-
rofive fublimate, and afterwards to dry the
portion of mercurius dulcis, which is then
found to be very mild. Mr. Cornet, to
avoid the noxious duft of the fublimate,
when triturated with mercury, propofes to
ufe the precipitate of mercurial nitre by
the volatile alkali, which unites much bet-
ter to corrofive fublimate than running mer-
cury ; but this precipitate not being as pure
as crude mercury, the preparation into which
it enters, cannot be fo much depended on.
Mr. Bailleau, apothecary at Paris, has com-
municated to the Royal Society of Medi-
cine, a procefs for making mercurius dulcis,
which is free from the imperfeftions and

danger

MERCURV. I45

danger of the common methods. It con-
fifts in forming a pafte of corrofive fubli-
mate and water, and triturating it with
running mercury; the trituration in the
courfe of half an, hour, caufes the mercury
to diiappear, becaufe the water promotes its
comminution, and the combination is com-
pleted by digefting the mixture on a fand
bath with a mild heat. The matter, which
at firft is grey, becomes white, and forms a
very mild mercurial muriate, which requires
only one fublimation to render it perfectly
pure.

Mr. Baume has made many experiments
on mercurius dulcis. He has proved that
this compound cannot be charged with a
'larger quantity of mercury, and that it can-
not exift in a middle ftate, between that of
corrofive fublimate, and perfect mercurius
dulcis : fo that when a fmaller quantity of
mercury is mixed with corrofive fublimate
than is neceflary to caufe it to pafs to the ftate
of mercurius dulcis, this laft compound is
formed in quantities proportioned to the
dofe of mercury added ; and the reft of the
fublimate is volatilized with all its proper-
ties, without being rendered at all milder.
The two compounds may be feparated by
means of warm water.

The experiments of the fame chemift like-
wife teach us, that it is poffible to change
mercurial dulcis into corrofive fublimate,

Vol. HI. K by

I46 MERCURY.

by fubliming it with decrepitated marine
fait and martial vitriol, calcined to white-
nefs. In this operation the marine acid,
being difengaged and dephlogifticated by
the oil of vitriol, feizes the calx of the
mercurius dulcis, and converts it into cor-
rofive fublimate. Mr. Baume has afcer-
tained another circumftance, which fhews
the great difference between mercurius dul-
cis and corrofive fublimate; namely, that
it does not unite with fal-ammoniac, as
fublimate does, in the preparation of fal-
alembroth. He therefore advifes the wafh-
ing of mercurius dulcis with water charged
with a fmall quantity of fal-ammoniac, in
order that all the corrofive fublimate may be
carried off. Laftly, he has difcovered, that
at each fublimation, the mercurius dulcis
lofes a portion of mercury, and confequent-
ly affords a fmall quantity of corrofive fub-
limate; fo that by repeated fublimations,
mercurius dulcis may be intirely changed
into corrofive fublimate. From this laft
experiment it obvioufly follows, that the
preparation known under the name of pana-
cea mercurialis, which is made by fublim-
ing mercurius dulcis nine times, is fo far
from being rendered milder by thefe opera-
tions, as molt chemifts and phyficians have
fuppofed, that it does not at all differ from
mercurius dulcis. This laft affertion is
eftabliflied the more incontrovertibly, by

the

MERCURY* 1^7

the circumftance of its being neceflary to
feparate a white powder which rifes the
firft in each fublimation, and is in fadt cor-
rofive fublimate. It muft be obferved, that
in the preparation of mercurius dulcis, a
reddifli powder remains in the bottles,
which is a calx of iron, afforded by the
martial vitriol ufed in the common method
of making corrofive fublimate for fale. A
portion of this calx rifes with the fait in
fublimation. Small pieces of glafs are like-
wife not unfrequently found, which have
been carried up by the vapours of the cor-
rofive fublimate.

The modern experiments made on the
dephlogifticated marine acid, tend greatly
to explain the theory of the formation of
mild mercurial muriate. It is now proved,
that corrofive mercurial muriate is a com-
pound of dephlogifticated or aerated muria-
tic acid, and the calx of mercury, and that
mild mercurial muriate is formed by com-"
mon muriatic acid, in combination with
the fame metallic calx. So that when run-
ning mercury is triturated with corrofive
mercurial muriate, it feizes the excefs of the
oxyginous principle from the dephlogifti-
cated muriatic acid, and by that means re-
duces it to theftateof common muriatic acid;
which diflblves a much larger quantity of
calx of mercury, than the fame acid fur-
charged with the oxyginous principle does.
K 2 The

I48 MERCURY.

The fedative acid does not immediately
diffolve mercury; but it has a very evident
action on that femi-metal, when in the cal-
ciform ftate. Thefe two fubftances may be
combined by the way of double affinity. A
folution of borax being poured into a ni-
trous folution of mercury, an abundant yel-
low precipitate is formed, as Mr. Monnet
firft obferved. In this operation the foda
of the borax unites with the nitrous acid,
and forms cubic nitre, while the acid of the
borax combines with the calx of mercury,
in the form of a neutral fait, which being
fparingly foluble, falls down. The filtrated
liquor affords, by evaporation, fine and bril-
liant pellicles of mercurial fedative fait,
which, by expofure to the air, become of
a greenifh hue. Sal-ammoniac renders this
fait very foluble, and forms with it a com-
pound, analogous to fal-alembroth ; lime-
water throws down a yellow precipitate,
which changes to deep red ; and vegetable
alkali caufes a white precipitate. Accord-
ing to the academicians of Dijon, the cor-
rofive mercurial muriate is likewife decom-
pofed by borax, which produces in its folu-
tion, a precipitate of a brick-duft colour.
Water, boiled on this precipitate, becomes
of a milky colour, by the addition of fixed
alkali, which proves that it contains mer-
curial fedative fait.

The

MERCURY. I49

The aflion of the fparry acid on mercury
is not known, and that of the cretaceous
.acid is almoft equally uncertain. It is only
known, that the acid fpirit of chalk does
riot attack this femi-metal ; but the folu-
tions of mercury decompofed by cretaceous
lime and alkalies, afford precipitates very
different from thole produced by the fame
fubflances when pure and cauflic.

Neutral falts have fcarcely any aftion on
mercury. Though this arlertion is more
efpecially applicable to the different vitriols,
I have obferved, neverthelefs, that mercury
becomes very quickly extinguifhed in vi-
Jriolated tartar.

Mercury does not appear capable of alter-
ing fal-ammoniac by diflillation. Bouquet,
who made this experiment, obferved, that
.two parts of mercury are not well extin-
guifhed by one part of fal-ammoniac, and
that the mixture does not afford volatile al-
kali by diflillation. The Count de la Ga-
raye, neverthelefs, prepared with thefe two
fubflances, a medicine, to which he gave
the name of tinfture of mercury. Macquer,
who examined his procefs, found it to
fucceed perfectly well. It con filled in tri-
turating one ounce of running mercury,
with four ounces of fal-ammoniac, in a
marble mortar, moiflening the mixture with
a fmall quantity of water, till the mercury
entirely difappeared. This matter being
K 3 left

jtQ MERCURY.

left expofed to the air five or fix weeks,
and from time to time agitated, is then to
be triturated afrefh, and afterwards expo-
fed in a matrafs on a fand bath, covering the
powder to the depth of about two inches
with good fpirit of wine. The mixture
being made to boil flowly, the fpirit of wine
affumes a yellow colour, and contains mer-
cury, as appears from its whitening a flip
of copper. From this experiment it ap-
pears, that the volatile alkali is gradually dif*
engaged by the mercury ; that fal-alembroth
is formed, part of which is diflblved by the
fpirit of wine j and that the different quan-
tity of the mercury, and the flow aftign pro-
duced during the maceration, are the caufes
of the difference between this experiment
and that of Bucquet.

The aftion of inflammable gas on mer-
cury is not known.

Mercury combines very readily with ful-
phur. When one part of this metallic fluid
is triturated with three parts of flowers of
fulphur, the mercury is gradually extin-
guished, and a black powder is produced,
which is called ^Ethiops mineral, and whofe
colour becomes deeper fome time after it is
made. This combination is more quickly
effected, by mixing mercury with melted
fulphur. The mixture being ftirred up im-
mediately, becomes black, and very readily
tak$s fire, When the ^thiops is perfectly

made,

MERCURY, I^I

made, it muft be taken from the fire, and the
matter mull: be kept ftirred till it becomes fo-
lid and in lumps. It muft then be pulveriz-
ed, and pafled through a fine fieve. The
,/Ethiops is not the mod intimate combi-
nation which fulphur and mercury are ca-
pable of forming. When this compound
is expofed to a confiderable degree of heat,
it takes fire, the greateft part of the fulphur
burns, and after the combuftion, a matter
remains, which, when pulverized, is of a
violet colour. To convert this powder in-
to cinnabar, it is put into matraffes, which
are heated till their bottoms become red,
and kept in this ftate for feveral hours, till
it appears that the matter is entirely fub-
limed. The artificial cinnabar is found
fublimed to the upper part of the matrafs,
in cryftalline needles, of a reddiih brown.
Cinnabar is of a lighter and more lively co-
lour, when fublimed in retorts. The Dutch
prepare in the large way, the cinnabar em-
ployed in the arts ; the compound is not
volatile, but requires a ftrong fire to fub-
lime it. When much divided by leviga-
tion, it has a brilliant red colour, and is
then called vermillion. If it be heated in
open veffels, the fulphur, which is not equal
to one fourth of its weight, burns gradu-
ally, and the mercury is volatilized. Many
fubftances are capable of decompofing cin-
nabar, by virtue of their affinity to fulphur.
K 4 Lime

I52 MERCURY'.

Lime and alkalies have this property ; when
thefe are heated in a retort, with twice their
weight of cinnabar, running mercury is ob-
tained, and the refidue is found to be liver
of fulphur. Mr. Baume has obferved, that
this decompofition takes place by the humid
way, when pounded cinnabar is boiled with
a folution of fixed alkali. It muft be ob-
ferved, that he employed the cretaceous al-
kali. Many femi-metals, fuch as cobalt,
bifmuth, and regulus of antimony, have
likewife the property of depriving mercury
of its fulphur. It will be hereafter feen,
that almoft all the metals, lead, tin, iron,
copper, and filver, have likewife a ftronger
affinity with fulphur than mercury, and
confequently decompofe cinnabar. They
may therefore be indifferently ufed, to fepa-
rate the mercury from this compound.
The metallic fluid obtained by thefe procef-
fes, is perfectly pure,, and is diftinguifhed
by the name of mercury revived from cin-
nabar.

Mercury immediately decompofes liver
of fulphur, but produces different phenome-
na, according to the nature of thefe com-
pounds. It forms j^Ethiops with the fix-
ed alkaline liver of fulphur $ and this
iEthiops, in the courfe of feveral years, be-
comes red. With the fuming liquor of
Boyle, it very quickly becomes converted
into iEthiops, and in a few hours, or 3t

moft

MERCURY* I53

mod: a few days, it affumes a brilliant red
colour, and affords a very firfe cinnabar.
Turbith mineral, precipitate per fe, red pre-
cipitate, and all the calces precipitated from
folutions of mercury by the alkalies, exhi-
bit the fame phenomenon, more or lefs rea-
dily, with the fuming liquor of Boyle. It
is likewife produced by pouring this liquor
into folutions of meicury, and expoiing the
black precipitate, which refults from thefe
mixtures, to a new quantity of volatile li-
ver of fulphur.

I have difcovered, that running mercury,
agitated in natural or artificial hepatifed wa-
ter, decompofes it very readily, and is chan-
ged into /Ethiops.

The aclion of mercury on regulus of arfe-
nic is not known. Cobalt does not unite
with it. Mercury diffolves bifmuth very
readily, with which it combines in all pro-
portions : from this combination a brilliant
friable matter is produced, which is more or
lefs folid, according to the quantity of bif-
muth it contains. This amalgam is capa-
ble of cryftailizing in four fided pyramids,
which fometimes unite together in octahe-
drons. But it mo ft commonly cryftallizes
in thin laminae, which have no regular form.
This cryftallization is obtained by melting
the combination, and fuffering it to cool
flowlv. When it is heated in a retort, it

does

I£4 MERCURY.

does not part with its mercury, but with
great difficulty.

Mercury does not unite either to nickel,
or to regulus of antimony. It combines
with zink by fufion. The amalgam form-
ed with this laft metal, is folid, but becomes
fluid by trituration. When melted, and fuf-
fered to cool flowly, it cryftallizes in lami-
nae, which appear fquare with rounded
edges.

Mercury is of the moft extenfive ufe in
the arts, fuch as gilding, filvering of glafles,
conftrudling of meteorological inftruments,
metallurgy, &c. it is ufed in medicine in a
great variety of forms.

i . Crude mercury was formerly employed
in the iliac pafiion. It is ftill boiled in water,
to which it communicates a vermifuge pro-
perty. Mixed with fat fubftances, it forms
an ointment, ufed in venereal diforders.

2. Turbith mineral has likewife been
recommended in the fame diforders, in the
dofe of a few grains. This medicine is eme-
tic and purgative.

3. Mercurial water is ufed by furgeons,
ps a powerful efcharotic. Red precipitate
anfwers the fame purpofe, A citron co-
loured ointment is prepared with hog's lard
and the nitrous folution of merqury, which
is a certain cure for the itch.

4. Corrofive fublimate has been recom-
mended by Sanches, and Van Swieten, in

venereal

MERCURY. 155

venereal diforders. A few grains are diflbl-
ved in brandy, and a fpoonful of this folution.
is taken at a time, in a large quantity of
mild liquid. The exhibition of this reme-
dy requires great care, more efpecially with
regard to the ftate of the ftomach and lungs.
Mercurius dulcis, given in the dofe of twelve
or fifteen grains, is a purgative, and in the
dofe of three or four grains, is an alterative.
The. phagedenic water is ufed in furgery,
to corrode and deftroy fungus, or proud
fle/h, &c.

5. Mercurial fedative falts have been ufed
with fuccefs in venereal diforders, by Mr.
Chauffier the younger, of the academy of
Dijon.

6. Cinnabar is confidered as an antispas-
modic and fedative medicine. It enters in-
to the compofition of the pulvis temperans
of Stahl, which is prepared according to the
Pharmacopeia of Paris, by accurately mix-
ing three grains of vitriolated tartar and ni-
tre, with two fcruples of artificial cinnabar.
This compound is (till ufed, by expofing
the patients to its vapour. It then confti-
tutes one of the methods of treatment of
venereal diforders, by fumigation.

All the preparations of mercury, which
are internally given, produce very beneficial
cffedls in other diforders, as well as thofe of
the venereal kind ; fuch as moft diforders
pf the fkin, fcrophulous diforders, lym-
phatic

I56 TIN,

phatic fwellings, &c. We cannot however
forbear obferving, that thefe medicines,
more efpecially the faline mercurial prepa-
rations, ought not to be applied but by ex-
perienced and cautious phyficians ; and that
it is dangerous to the health, and even to
the life of men, that mercurial remedies
fhould be in the hands of a great number
of perfons, who, generally fpeaking, are de-
ficient, not only in the knowledge which
is neceflary to adminifter them with fuccefs,
but even in that knowledge which might en??
able them to avoid danger. I have myfelf
been more than once witnefs to the unhappy
effe&s of thefe preparations, caufed by the
unfkilfulnefs of thofe who have employed
them with that rafhnefs which commonly
accompanies ignorance. This fubjedl ap-r
pears to be of fufficient importance, to de-r
ferve the attention of the legiflature.

CHAP. XV.
Concerning Tin.

^TMN, or Jupiter of the alchymifts, is ap
■* imperfecft metal, of a whiter colour
than lead, but not quite fo white as filver,
It is eafily bent, and produces a crackling
noife when bent; a phenomenon which we
have already oWerved, though lefs evident-

TIN*. 157

]y, in zink, and which has been urged by
Malouin, as an inftance of Similarity be-
tween that femi-metal and tin.

This noife appears to depend on the Sud-
den feparation of the parts of the metal, and
Seems to mew, that a fracture takes pl?ce,
though tin refills very little the effort which
is made to bend it.

Tin is the lighten: of all metals; it is
Sufficiently foft to be Scratched with the
nail. In water it lofes about, one feventh
of its weight. It has evidently a fmell,
which becomes much Stronger by heating
or rubbing. It lias likewife a peculiarly dis-
agreeable tafte, lb flrong, that fome phyfi-
cians have fuppofed it to have a feniible
action on the animal ceconomy, and conse-
quently have recommended it in feveral
diSorders. Its extreme foftnefs renders it
fcarcely at all lbnorous. Tin is the fecond
among metals, in the order of ductility ; it is
reducible beneath the hammer into lamina?,
thinner than leaves of paper, which are of
great ufe in many arts. Its toughnefs is fuch,
that a wire of tin, of the tenth of an inch in
diameter, fupports a weight of forty-nine
pounds and a half without breaking. The
Abbe Mongez did not fucceed in his at-
tempts to cryftallize tin ; but Mr. De la
Chenoye, one of my pupils, has Succeed-
ed, by fufing the tin for a number of fuc-
ceflive times, by which means he obtained

a rhom-

158 TIN.

a rhomboidal aflemblage of prifms or needles,
united longitudinally to each other.

Moft mineralogifts ftill doubt the exift-
ence of native tin ; fome authors however
affirm, that it has been found in Saxony,
in Bohemia, and in the peninfula of Malac-
ca. It is ftrongly affirmed, that it exifts in
the mines of Cornwall -y and Mr. Sage has
defcribed a fpecimen of this tin given him,
by Mr. Woulfe, a chemift of London. This
piece is grey and brilliant in its frafture ;
when beaten on the anvil, it forms brilliant
and flexible laminas. Tin is more common-
ly met with in a white ponderous opake
calx, cryftallized in octahedrons, or four
lided pyramids; its texture is lamellated
and fparry. Bucquet confiders it as a true
fpar of tin. Sage thinks that thefe cryftals
are mineralized by the muriatic acid ; per-
haps, like the fpathofe ore of iron, they
may be a combination of the calx of tin,
and the cretaceous acid. This white ore
of tin was clafled among the ores of iron
by Cronftedt.

The appellation of tin ore is given more
efpecially to bodies of a very deep red, vio-
let, or black colour, and of more confidera-
ble weight than any other mineral fub-
ftance. Thefe ores are fometimes cryftal-
lized in regular cubes, and exhibit groups,
difperfed on a bed of quartz, or fuflble
ibar ; they very frequently form mafles,

without

TIN. I59

without any other cryftallization. Moft
naturalifts agree in fuppofing the coloured
ores of tin to be combinations of this me-
tal with arfenic, and they attribute their ex-
ceffive weight to the abfence of fulphur.
Meflrs. Sage and Kirwan think however,
that they do not contain any arfenic ; and
the former affirms, that it is not neceflary
to roaft them, unlefs they be mixed with
arfenical pyrites, which is a very common,
circumftance. Bergman admits the exift-
ence of fulphurated tin in nature among
the minerals of Siberia. This fulphureous
ore was externally of a golden colour, like
aurum mufivum, and its internal part pre-
fented a mafs of radiated cryftals, white,
brilliant, and brittle, and affuming change-
able colours on expofure to air. It con-
tained a fmall portion of copper.

There have been no mines of tin found
in France. Mr. Baume however fufpedts,
that it might be found in the neighbour-
hood of Alenfon, and in fome cantons of
Britany, becaufe rock cryftals are found,
which appear to be coloured by that metal.
The countries where they are the moft abun-
dant, and are worked, are the counties of
Cornwall and Devonfhire, in England; Ger-
many, Bohemia, Saxony, the Ifland of Ban-
ca, and the Peninfula of Malacca, in the
Eaft-Indies. Many naturalifts have con-
iidered garnets as ores of tin, doubtlefs on

account

160 TIN.

account of their colour ; they differ however
from tin ores, by their tranfparency and their
weight, which laft is much lefs. Meffrs.
Bucquet and Sage have not found that they
contain tin.

The different ftates of tin found in na-
ture, are not therefore numerous, and may
be reduced to the following varieties.

Varieties.

1. Native tin in leaves or plates.

2. White fpathofe tin ore, in octahedral

cryftals.

3. Tin ore of a yellowifh white; often

coloured and femi-tranfparent, like
topazes. Thefe two ores muft not
be confounded with the heavy ftone,
or tungften of the Swedes, which
we have defcribed at the end of the
falts, and has the property of be-
coming yellow by the nitrous and
muriatic acids.

4. Brown or reddifh tin ore, in cubical

cryftals, more or lefs regular.

5. Tin ftone, tinberg of the Swedes; it

is a ftone or fand, which contains a
mixture of calx of tin. The fpe-
cimens are grey, blue, brown, and
black.

6. Sulphureous ore of tin, of a brilliant

colour, fimilar to that of zink, or
golden, like aurum mufivum.

To

TIN* l6t

To make the afiay of an ore of tin, it muft:
be grofsly pounded, after dividing it into
different parcels, washed and roafted in a
covered capfule of earth, care being taken
to uncover it from time to time, in order to
diffipate the tin as little as poffible ; for if
it be roafted in an open fire, much of that
metal is loft, as Cramer remarks. It muft
likewife be roafted with expedition, left the
tin fhould be too much calcined. Mr.
Baume, to obviate thefe two inconveniences,
propofes to mix a quantity of rofin or pitch,
which reduces a portion of the calx formed
in this operation. After the ore is roafted,
it is to be quickly fufed in the crucible, with
three parts of black flux, and a fmall quan-
tity of decrepitated marine fait. By com-
paring the weight of the ore with that of
the metallic button obtained, the quantity
of foreign matter, and the proportion of tin
it will afford in the hundred, is known.
Cramer propofes to make this affay in a more
expeditious manner, and perhaps with lefs
lofs, by making ufe of two large pieces of
charcoal; one of them muft have a cavity,
to ferve inftead of a crucible, into which the
ore is put, with a fufficient quantity of pitch.
The other is perforated with a fmall open-
ing, to give iflue to the vapours. This is
applied on the former to cover it, and they
are tied together with iron wire, after hav-
ing luted the joinings. Thefe are fet on
Vol. III. L fire

}6z TIN.

means of charcoal placed round them. As
foon as a fufficient heat has been given to
fufe the tin, the charcoal is to be extinguilh-
ed with water, and the tin is found within
them, in the form of a button or globule.

Bergman propofes to allay the ores of tin
by folution in vitriolic acid, to which the
muriatic acid is afterwards added * and to
precipitate it by fixed alkali. If the tin be
pure, one hundred and thirty-one grains of
the precipitate will be equal to one hun-
dred and fix of tin. If it be mixed with
copper and iron, thefe foreign metals are to
be removed by means of the nitrous and
muriatic acids.

The working of ores of tin in the large
way, is fimilar to the procefs before defcri-
bed ; it is often neceffary to make fires of
wood in the mine, to calcine and foften the
gangue, which is very hard, by which very
dangerous vapours are difengaged. This
procefs is ufed in the mines of Geyer. In
other places the ores are found in fand, at
a very fmall depth, as at Ebenftock. The
pounded ore is warned in boxes, with little
partitions of cloth, to retain the metallic
particles ; it is then roafted in reverbera-
tory furnaces, to which a horizontal chim-
ney is adapted, to collect the fulphur and
arfenic; after which it is fufed, and poured
into moulds, to give it the form of blocks.
The ores of tin are wrought nearly in the
fame way in Germany and in England. In

the

TIN. 163

the latter country, this metal is alloyed with
lead and copper, according to GeorTroy, and
never exported in a ftate of purity. We
likewife receive from England, a kind of tin
in ftalactites, which is called grain tin, which
is thought to be very pure; but Meffrs.
Bayen and Charlard affirm, that it fometimes
contains copper. The pureft tin of all is that
which comes from Malacca and Banca ;
the firft has been run into moulds, which
give it the form of a quadrangular truncated
pyramid, with a narrow flope round its bafe,
each ingot weighs about a pound. The fe-
cond is in oblong ingots, weighing forty-five
or fifty pounds ; thefe two kinds of tin are
covered with a grey ruft, more or lefs thick.
The tin which comes from England/ and
is much more ufed than the pure tin of the
Indies, its price being lower, is in the
form of large blocks, of about three hun-
dred pounds weight. It is alloyed with cop-
per, either artificially, according to Geoffroy,
or naturally, according to Baron Dietrich.
To facilitate the fale, it is afterwards melt-
ed into lmall ingots, or flicks, of nine or
ten lines in circumference, and about afoot
and a half long.*

* Englifh tin being the moll generally ufed, on account
of its plenty, is the moft generally adulterated by the foreign
venders. It is a vulgar error among foreigners, that pure
tin is not permitted to be exported hence. According to
Neumann, every tin founder in Holland has Englifti ftamp?,
and whatever his tin may be, the infeription block tin makes
it pafs.

L 2 Tin

164 TIN-

Tin expofed to heat in clofe veiTels, melts
very quickly. It is the mofl fufible of
metals, and remains fixed as long as the fire
is not raifed ; but this fixity appears to be
only relative, fince a confiderable heat vola-
tilizes it, as we fhall fhortly obferve. It is
to be heated with accefs of air; its furface
becomes covered with a dull greyifh pelli-
cle. When this is taken away, the tin is
feen underneath with all its metallic bril-
liancy. A new pellicle fuon becomes col-
lected, and in this manner all the tin may be
reduced into pellicles, which ' are nothing
elfe but a metallic calx, or combination of
the metal with the bafe of vital air. Tin
becomes one tenth heavier by calcination.
If the metal be heated to rednefs, GeofFroy
has obferved, that its calx is gradually raif-
ed by a very lively whitifh flame, which he
compares to that of zink. This is a true
inflammation, or rapid combuflion of the
metal, at the fame time that a light fume of
tin is volatilized, which is condenfed on
cold bodies, into a whitifh calx, in the form
of needles or flowers of tin. The grey calx
of tin becomes white, if again expofed to
the adion of a flrong fire ; it unites to an
additional quantity of the oxyginous prin-
ciple, and becomes more calcined. In this
flate it is called putty. If it be expofed
to an exceedingly ftrong heat, as for exam-
ple, that of a porcelain furnace, it melts

into

TIN. 165

into glafs. Meflrs. Macquer and Baume
have obferved, that tin thus treated in a
crucible, is converted intoa white and needle-
formed calx, or flowers of tin, and the part
underneath is hard, coherent, reddiih, and
imperfectly melted calx; that another part
forms a glafs of the colour of a ruby or hya-
cinth -, and that laftly, at the bottom of the
crucible a part of the tin remains in the me-
tallic ftate. Calx of tin requires a fire of
the utmoft violence to melt it into glafs ;
the calx or putty may be decompofed by the
addition of animal or vegetable combufti-
ble matters, which feize the oxyginous prin-
ciple contained in the calx, and caufe the
metal to re-appear with all its properties.
It feems, however, that well calcined putty
ftrongly retains the bafe of air to which it is
united, fince it is not reduced but with great
difficulty, and by the addition of a large
quantity of combuftible matter. Hence it
is, that Meflrs. Baume and other chemifts
have concluded, that when tin ores are too
much roafted, a portion is converted into a
calx no longer reducible into metal.

Tin is not much altered by expofure to
air, and does not readily become tarniflied
when it is pure. The tin of commerce is
covered, after a certain time, with a grey
powder, which, according to Macquer, is
merely fuperficial, and never penetrates into
L 3 the

166 TIN.

the metal, as the ruft of copper and iron
does.

Water does not difiblve or calcine tin,
though in procefs of time it tarnifhes its
furface.

Earthy matters contract no union with
this metal. Its calx, which is very infun>
ble, does not form a tranfparent, nor colour-
ed glafs with vitrifying fubftances ; but as
it is exceedingly white, it renders the glafs
of a very opake white colour, by its inter-
polition between the tranfparent parts. This
kind of vitreous frit is called enamel. Putty
of tin, on account of its infufibility, deprives
all glaffes of their tranfparency, and con-
verts them into coloured enamels.

The aftion of lime, magnefia, and alkalies
on tin, has not been inquired into. It can-
not, however, be doubted, but the latter falts
are capable of producing fome change in the
metal, fince in a very fhort time they caufe
it to exhibit the colours of the rainbow.

The concentrated vitriolic acid, or oil of
vitriol, according to Kunckel, diflblves half
its weight of tin. The folution is perform-
ed very well by the affiflance of heat. Sul-
phureous gas, of a very penetrating fmell, is
difengaged, without any apparent effervef-
cence or motion. The tin, in this experi-
ment, feizes the oxyginous principle of the
vitriolic acid, becomes quickly calcined, and
the oil of vitriol is found to contain a fuf-

ficient

TIN. 167

ficient quantity of the calx, to afford a pre-
cipitate by the addition of water. Oil of
vitriol diluted with a fmall quantity of wa-
ter acls likewife on tin, but the folution is
more permanent, and affords a lefs abundant
precipitate on the addition of more water.
Spirit of vitriol, or feeble vitriolic acid,
does not diffolve it. In this combination
the tin feizes the oxyginous principle of the
oil of vitriol, in fuch quantities, that fulphur
is verv fuddenlv formed. This fubftance
gives the folution a brown colour while it
is warm, and is precipitated as foon as it
becomes cold. Meffrs. Macquer and Baume
have afcertained the prefence of fulphur in
this combination. When the folution is
more ftrongly heated, the tin is precipitated
in the form of a white calx. The fame
phenomenon takes place without the affift-
anceof heat, though in a much longer time.
Tin dillblved in the vitriolic acid, is very
cauftic. Mr. Monnet, by cooling, obtained
cryftals fimilar to felenite, or fine needles,
intermixed with each other. The calx of
tin precipitated from its folution by ftand-
ing, or by heat, is foluble in the vitriolic
acid. If the vitriolic folution of tin be eva-
porated to drynefs, the calx it affords is of
a grey colour, very difficult of reduction,
and no longer foluble in the acid. Alkalies
precipitate tin from the vitriolic acid, in the
form of a very white ca!x.

L 4 Nitrous

168 TIN,

Nitrous acid is decompofed by tin, with
a Angular degree of rapidity. Heat is not
neceffary to promote this folution, which is
one of the mod rapid and ftriking among
chemical phenomena. It appears, that the
tin has a very ftrong tendency to unite with
the oxyginous principle of the nitrous acid •>
and as nitrous gas is far from adhering as
ftrongly to the pure oxyginous principle in
this acid, as fulphur to the fame principle
in the acid of vitriol, it is not furprizing
that the decompofition of the former, by
tin, fhould be much quicker than that of
the latter, by the fame metal. A large
quantity of very ftrong nitrous gas is difen-
gaged with the greateft rapidity. I have
obferved, that this combination conftitutes
one of the mod advantageous methods, of
inftantly obtaining a large quantity of this
gas. The tin is converted into a white
powder or calx, which Macquer in vain at-
tempted to reduce. The metal in this ftatc
appears to be fuperfaturated with the oxy~
ginous principle. The nitrous acid holds
but a very fmall quantity of the metal in
folution ', and when evaporated with the
intention of obtaining cryftals, the diflblved
portion quickly precipitates, and the acid
remains nearly in a ftate of purity. Buc-
quet however affirms, that a nitre of tin,
whofe form he has not determined, may
be obtained from this folution ; it is very

deliquefcent.

TIN. 169

deliquefcent. He likewife aflerts, that if
the calx of tin, produced by the decompo-
sition of the nitrous acid, be wafhed with
water, the fluid diflblves a fmall quantity of
nitre of tin, which may be obtained by eva-
poration. The nitrous acid retains a fome-
what larger quantity of tin in folution, when
it is ufed in a very diluted ftate; but it lets
it fall by (landing, or by the application of
heat. Meflfrs. Bayen andCharland, in their
valuable inquiries concerning tin, have dif-
covered, that when the nitrous acid is char-
ged with all the tin it can calcine, fo as to
become thick and incapable of adting on
new portions of the metal, a nitrous fait
is obtained, by wafhing the mafs with a
large quantity of diililled water, and eva-
porating the water to drynefs, which fait
detonates alone in a heated veflfel, and burns
with a white and denfe flame, like that of
phofphorus. The calx of tin well wafhed,
affords when dry, a femi-tranfparent mafs,
refembling fcales. The ftanonitrous felt
diftilled in a retort, fwells up, boils, and
inftantly fills the receiver with a white thick
vapour, of a nitrous fmell.

The fuming muriatic acid afts ftrongly
on tin, and diflblves it by the help of a gen-
tle heat, and even in the cold ; inftantly
loiing its colour and property of emitting
fumes. The very flight effervefcence which
takes place in this combination, difengages

a fetid

170 TIN.

a fetid gas from the mixture, not at all re-*
fembling the fmell of arfenic, as fome che-
mifts have affirmed. The muriatic acid
diffolves more than half its weight of tin ;
the folution is yellowifh, of a very fetid
fmell, and does not afford a fpontaneous pre-
cipitate like the two laft mentioned acids.
By evaporation it affords brilliant and very
regularly formed needles, which flightly at-
tract the humidity of the air., Mr. Monnet
affirms, that thefe needles, after having de-
liquiated, cryftallize, and remain dry in the
air. M. Baume, who prepared the muri-
ate of tin in the large way, as for example,
in the proportion of one hundred and fifty
pounds of acid to twenty-five pounds of tin,
for the manufacture of painted filks, has
accurately defcribed fome of its properties.
Out of two pounds of tin diffolved in forty-
eight pounds of muriatic acid, there remain-
ed two ounces fix drachms of a grey pow-
der, not foluble in one pound of the acid,
with which he digefted it for feveral days.
Margrafftakesittobe arfenic, but M. Baume
did not examine it. He compares the fmell
of this concentrated folution to that of the
black earths taken out of old fewers, and
remarks, that when it touches the fingers,
nothing can take away the metallic fmell
peculiar to tin, which it communicates to
them, and which is not diffipated in lefs
than twenty-four hours. He obferves, that

the

TI\T. 171

the cryftals of t'he muriate of tin vary ac-
cording to the ftate of the acid. In fome
cafes they form fmall white needles ; and
the fame folution as afforded him white and
rofe coloured cryftals. The latter, purified
by folution and evaporation, afforded, by
cooling, large cryftals, nearly limilar to thofe
of the vitriol of foda. Another time, when
the common muriatic acid was ufed, he ob-
tained the fait in the form of fmall fcales,
of a pearly white, iimilar to that of fedative
fait. He does not fpeak of the action of fire
on this fait. Mr. Monnet, who diflilled
the muriatic folution of tin, affirms that
he obtained a fat matter, very fuiible, and
readily congealing, and afterwards a true
butter of tin, with a fuming liquor fimilar
to that of Libavius, hereafter to be mention-
ed. This fact agrees with the obfervation
made by Macquer on a folution of tin in
the muriatic acid, which cryftallized almoft
totally during the winter, and recovered its
fluidity in fummcr; a property likewife ob-
fervable in butter of tin. This illuftrious
chemift remarked, that a white depofition
fubfided at the end of fome years. The
combination of the muriatic acid and tin,
affords a much more abundant precipitate
than other folutions, on the addition of al-
kalies and lime. Alkalies re-diffolve a part
of the precipitated calx, and affume a yellow
brown colour. It was by diliblving a va-
riety

I72 TIN.

riety of fpecimens of impure tin in this acid,
that Meflrs. Bayen and Charlard fucceeded
in difcovering a fmall proportion of regulus
ofarfenic in the Englifh tin. When this
femi-metal is contained in tin, the adlion of
the acid produces a black colour in the me-
tal, and when the folution is finifhed, a
blackifh powder remains, which is arfenic,
either pure, or united to a fmall quantity of
copper. This acid therefore may be ufed
to difcover the prefence and quantity of re-
gulus ofarfenic contained in tin.

The dephlogifticated muriatic acid, dif-
folves tin very readily, and without fenfible
effervefcence, becaufe that metal quickly ab-
forbs the fuper-abundant oxyginous princi-
ple from the acid, and does not require any
decompofition of the acid to effedl its own
calcination. The folution has then all the
character: of the preceding.

Aqua regia, made with two parts of ni-
trous acid, and one of muriatic acid, diffol-
ves tin with effervefcence. A ftrong heat
is excited, which muft be checked by plun-
ging the mixture into cold water. To form
a permanent folution of tin in aqua regia,
the metal muft be added by fmall portions
at a time ; one portion being fufrered intire-
ly to difappear, before a fucceeding one be
added; if the whole were added at once,
great part of the metal would be calcined.
Aqua regia, by this management, will dif-

folve

TIN. 173

folve half its weight of tin. The folution
is of a reddifh brown, nearly tranfparent,
and frequently, in a few feconds, becomes
converted into a tremulous jelly, of the ap-
pearance of rofin. This fubftance becomes
more folid at the end of a few days, and
may be cut in pieces like a firm animal jelly.
Some parts exhibit the femi- tranfparency
and whitenefs of the opal. It emits a pe-
netrating fmell of marine acid, but is not
fetid like the muriatic folution. I have pre-
ferved it feveral years in a bottle, imperfect-
ly clofed, and found that it has not loft any
part of its folidity or tranfparency. In order
that the folution of tin, by aqua regia, may
form a jelly, it muft be charged with a large
proportion of metal. Sometimes it becomes
concrete, on the addition of half its weight
of water, though it was perfectly fluid be-
fore : but the jelly formed by the addition
of water, is of an opal colour, becaufc, ac-
cording to the remark of Macquer, the fo-
lution itfelf being decompofable by water,
a portion of the calx of tin is precipitated,
and deftroys the tranfparency of the jelly.
This learned chemift has likewife obferved,
that if a folution of tin in aqua regia be
heated, an effervefcence is excited, which
arifes from the re-action of the mixed acid
on the metal, its whole action not being
already exhaufted. The folution then lofes
all its colour, and becomes fixed by cooling.

The

174 tin*

The jelly it forms in this cafe, is beautifully
tranfparent. Small needle-formed cryftals
are frequently depofited from a regaline and
liquid folution of tin by {landing. Neither
thefe, nor the gas difengaged during the
action of aqua regia on tin, have been yet
examined. Meffrs. Bayen and Charlard
find, that this folvent might likewife be ufed
to difcover the prefence of regulus of arfe-
nic in tin, if its action on the femi-metal
were lefs coniiderable. But this circum-
ftance prevents its indicating the quantity
with the fame precifion as the muriatic
acid.

The action of other acids on tin is not
known.

All the neutral vitriolic falts, and efpeci-
ally vitriolated tartar and Glauber's fait, are
decompofed by tin. Equal parts of vitrio-
lated tartar and tin being heated in a cruci-
ble, afforded me a greenifh melted mafs,
which no longer exhibited any metal, and
was a true liver of tin. The tin deprives
the vitriolic acid of its oxyginous principle,
the fulphur formed by this decompofition,
becomes hepatic by the action of the alkali,
and this hepar diflblves a portion of the
calx of tin. It is the third metallic fub-
ftance, in which we have obferved this pro-
perty of decompofing alkaline vitriols. We
(hall prefently find, that Glauber made the
fame obfervation on the ammoniacal vitriol.

This

TIN. 175

This metal caufes nitre to detonate with
rapidity. For this purpofe it is melted, and
made obfcurely red hot in a crucible. Com-
mon nitre in powder being then thrown in,
produces a white and brilliant flame. The
tin, when the addition of nitre no longer
produces detonation, is intirely calcined.
The white powder which remains, contains
alkali, rendered cauftic by the calx of tin,
and united to a certain quantity of that
calx. By lixiviation, and the addition of
an acid, the tin may be precipitated.
The grey calx of tin is fufible with nitre,
becaufe, as GeofFroy has obferved, it con-
tains a portion of tin, which is only in a
ftate of extreme diviiion. If a perfed: calx
of this metal be taken, as for example, fuch
as has been long heated, and is very white ;
or inftead thereof, fuch a calx as is afforded
by acids, the fame phenomenon does not
follow.

Tin very readily decompofes ammoniacal
muriate, and difengages a very cauftic and
gafeous volatile alkali. Bucquet, who made
a courfe of jexperiments on the decompofi-
tion of fal-ammoniac by metallic fubflances
and their calces, obferves, that much inflam-
mable gas is difengaged by the re-aftion of
tin on the marine acid. According to the
experiments of this learned chemift, metals
decompofe this fait, by virtue of the aftion
of the muriatic acid on them : and as we

have

I76 TIN.

have feen, that the marine acid has a very
ftrong affinity with tin, it may be conclud-
ed, that the theory of Bucquet is fatisfac-
tory and perfe&ly confonant with the fadts.
Glauber informs us, that his fecret fal am-
moniac, or ammonical vitriol, is decompos-
ed by tin $ but this decompofition is not
complete, according to Pott, who repeated
Glaubers experiment ; doubtlefs becaufe
the vitriolic acid has not foftrong an affinity
with tin as the muriatic. But he likewife
obferves, that the tin being very fufible, is
colle&ed in a button at the bottom of the
retort, and that confequently, the ammoni-
cal muriate is not fo completely decompofed
as otherwife it might be by the metal. For
this reafon tin does not decompofe this fait
as perfectly as lefs fufible metals. The re-
fidue of the decompofition is a corneous tin
or butter of tin, decompofable by water,
and fimilar to that which is formed by this
metal with corrofive fublimate, hereafter to
be treated of.

Tin may be eafily combined with fulphur,
by throwing one or two parts of fulphur in
powder, on five or fix parts of tin melted in
an iron ladle. The mixture being agitated
with an iron fpatula, becomes black, and
takes fire. If it be melted in a crucible, a
brittle mafs, difpofed in flat needles united
together, is obtained. This combination is
much more difficult to melt than tin, a

property

TIN, I77

property common to all combinations of
foft and fufible metals with fulphur. But the
moft important circumftance is, that though
tin eaiily unites with fulphur by fufion, it is
never found naturally in this ftate. The
faft is abfolutely the contrary with zink,
which is frequently combined with fulphur
in its ores, though it does not unite with it
in our laboratories without the greater!: diffi-
culty. The operations of nature are often
very different from thofe of art ; but though
fome natural combinations are found, which
art has not fucceeded in imitating, it is like-
wife certain, that many compofitions are ar-
tificially produced, of which nature furnifhes
no model.

Arfenic fcarcely unites with tin by fufion,
becaufe the greater part is diffipated. The
neutral arfenical fait combines better with
that metal 5 and M. Baume has obferved,
that in this combination, the arfenic quit-
ting the alkali to unite with the tin, pro-
duces a brittle brilliant button, difpofed in
facets like the regulus of antimony. The
experiments which MargrafT has made con-
cerning the union of tin with arfenic, by
diftillation, have fhewn us, that part of the
arfenic is reduced into the reguline form,
while a portion of the tin is calcined. The
tin thus united to arfenic, is not feparable
by the action of the moft violent fire, and it
is probable the former metal always retains
Vol, III. M a portion

178 TIN.

a portion of arfenic, fufficient to render its ufc
dangerous in culinary operations. When
the calx of tin, charged with arfenic, is ex-
pofed to diftillation, a fmall quantity of li-
quid, which has the fmell of phofphorus, is
obtained, according to Margraff. MefTrs.
Bayen and Charlard have, fince his time,
examined the combination of arfenic and
tin. They obferve, that the calx of arfenic,
called fimply, arfenic, does not combine
with tin, but in proportion as it acquires
the metallic flate ; and that this combination
is effected much better, by directly uniting
the regulus of arfenic with tin. If three
ounces fix drachms of tin be put into a re-
tort, with two drachms of regulus of arfe-
nic in coarfe powder, and the retort, after
adapting a receiver, be heated to rednefs,
fcarcely two grains of arfenic are elevated
in the neck of the veffel, and a metallic but-
ton, weighing four ounces, is found at the
bottom of the retort. This alloy, which
contains one fixteenth of its weight of re-
gulus of arfenic, is cryftallized in large fa-
cets, like bifmuth. It is more brittle than
zink, and lefs fufible than tin. It firft be-
comes foft by heat, and if in this flate it be
touched with an iron rod, a crackling noife
is produced by the friction of its laminae on
each other. It melts into the confiftence of
pafte, and gradually emits the regulus of
arfenic in the form of fumes.

Cobalt

TIN. I79

. Cobalt unites by fufion to tin, and forms
an alloy in (mail dole grains, of a light vio-
let colour.

Tin and bifmuth afford, according to
Geliert, a brittle alloy, prefenting cubic fa-
cets in its fracture. Tin is fometimes al-
loyed with this laft metal, to give it white-
nefs and hardnefs. As it communicates a
great degree of firmnefs, and is dearer than
zink, which produces the fame effects 011
tin, workmen cannot be fuppofed to employ
it in a larger proportion than a pound, or a
pound and a half in the hundred, in which
cafe, its effects on the animal ceconomy need
not be feared. But in larger proportions
they might be fufpected to referable thofe
of lead, from the iirong affinity between <he
properties of bifmuth and that metal. Bif-
muth may be feparated from tin by the ma-
rine acid, which diffolves the latter, and
fuffers the former to precipitate in a black
powder, provided the acid be weak. Aqua
regia, diluted with water, produces the fame
effect.

Regulus of antimony, united to this me-
tal, affords, according to Geliert, a white and
very brittle metal, whofe fpecific gravity is
lefs than that of the two metallic fubftances
taken feparately.

Zink unites perfectly with tin, and pro-
duces a hard metal of a clofe grained frac-
M 2 ture,

l8o TIN.

ture, and more duftile in proportion as the
quantity of tin is larger.

Cronftedt affirms, that nickel united to
tin forms a white and brilliant mafs, which
when calcined under a muffle, rifes in the
form of a vegetation.

Mercury diffolves tin with great facility,
and in all proportions. To make this com-
bination, heated mercury is poured on melt-
ed tin ; the amalgama produced, differs in
its folidity according to the relative dofes
of thefe two metallic fubftances. An am-
algam was formerly made with four parts of
tin, and one of mercury, which were caft
into balls that became folid in cooling ;
thefe balls were fufpended in water for the
puipofe of purifying it : but as the water
was at the fame time made to boil, the pre-
cipitation of foreign fubftances, which con-
taminated the water, was intirely owing to
the laft circumftance, and not to the me-
tallic fubftance. The amalgama of tin is
capable of cryftallizing, and has the form
of fmall cubes, as Mr. Daubenton obferved
in the amalgam of tin ufed by him to clofe
the mouths of veffels containing prepara-
tions in the King's garden. Mr. Sage
affirms, that the cryftals are grey, brilliant,
and in plated laminae, thin towards their
edges, and that the cavities between them
are polygonal.

Tin has a flronger affinity with the muri-
atic acid than mercury, and decompofes the

CQrrofive

TIN I 8 I

corroilve mercurial muriate. To effefl: this,
the tin is firft divided by the addition of a
fmall portion of mercury ; equal parts of
this amalagam, and the corrofive mercurial
muriate are triturated together, and the mix-
ture expofed to diftillation in a glafs retort,
by a very gentle heat- A colourlefs liquor
firft paries over, and is followed by a thick
white vapour, which iffues with a kind of
explofion, and covers the internal furface of
the receiver with a very thin crufl. The
vapour becomes condenied into a tranfpa-
rent liquor, which continually emits a thick,
white, and very abundant fume. It is cal-
led the fuming liquor of Libavius, and is
the combination of the muriatic acid and
tin, the acid appearing to be fuperfaturated
with the oxyginous principle. This liquor,
when clofed in a bottle, does not emit vifi-
ble vapours, though a certain quantity is
difengaged, which depolits the calx of tin
in needle-formed cryftals, at the upper part
of the bottle ; fo that the extremity of the
neck becomes accurately clofed at the end of
fome months. A fmall portion of this calx
is likewife precipitated to the bottom of the
liquor, in the form of regular fcales. The
fmell of this fluid, which is very penetrat-
ing, excites coughing : the vapours are not
vifible without contact of air, and feem to
confift of a peculiar gas, decompofahle by
air, which in that cafe depofits the calx of

M 3 tin,

l82 TIN.

tin, in the fame manner as the fparry acid
depofits quartzofe earth by the contact of
water, and as the hepatic gas of Bergman
depofits fulphur by the contact of air.
May not this elaftic fluid be a combination
of the dephlogifticated muriatic gas and calx
of tin ?

Water does not fenfibly precipitate the
fuming liquor of Libavius, but feems to
effect a decompofition, which has not yet
been properly examined. When this li-
quor, newly prepared, is poured into diftil-
led water, it occafions a flight noife, re-
fembling that of oil of vitriol, during its
union with the fame fluid. It appears to fe-
parate a great number of fmall tranfparent
particles, of an irregular figure, which do
not feem to have any affinity with water.
On a clofer attention to the mixture, each
of thefe particles is obferved to emit a bub-
ble, which breaks at the furface of the wa-
ter, and emits a vapour, which becomes
white by the contact of air. On agitating
the water, thefe particles are very quickly
difiblved, and the folution no longer emits
vapours. Macquer affirms, that when the
fuming liquor of Libavius is diluted with
a large quantity of water, it precipitates the
calx of tin in fmall white flocks. The gas
of the fuming liquor is not very elaftic, as
it never caufes the ftopper of the bottle, in
which it is clofed, to fly out, as happens

occafionally

TIN. 183

occafionally to the nitrous and marine acids,
the volatile alkali, ether, &c.

The refidue of the distillation of the
fuming liquor of Libavius, exhibits pheno-
mena equally interesting with thofe of the
liquor itfelf. The upper part and the neck
of the retort, are covered with alight, white
and greyifh cruft, which, according to the
experiments of Rouelle the younger, con-
tains a fmall quantity of the fuming liquor,
corneous tin, mercurius dulcis, and running
mercury : the bottom of the veiiel contains
an amalgam of mercury and tin, above which
is a corneous tin of a light grey, folid and
compact, which may be volatilized by a
ftronger heat. If this fubftance be put into
a retort, it melts, and is feparated into two
diftind: fubftances, the one black, and lying
beneath the other, which is white, and re-
fembles corneous tin. The name of butter
of tin might perhaps be applied more pro-
perly than that of corneous tin, to thefe
combinations. Rouelle appears to fufpect
that thefe two fubftances, which differ from
eath other, and do not mix, arife from the
tin being alloyed with fome other metal ;
the more the tin is alloyed, the fmaller the
quantity of fuming liquor it affords, accord-
ing to this fkilful chemift. Corneous tin
attracts the moiilure of the air, and is ea-
fily foluble in water; which diftinguifhes it
from corneous lead. M. Baume has pub-

M 4 liflied

184 TIN,

lifhed a theory refpe&ing the combination
of tin with the marine acid, which nearly
refembles that of Scheele and Bergman, con-
cerning the dephlogifticated marine acid.
He thinks that this acid lofes its phlogifton
in the operation, as thofe chemifts fup-
pofed likewife to happen in the diftillation
with calx of 'manganefe. He fufpefts that
this acid would be obtained perfectly pure,
by diftilling the fuming liquor of Libavius.
Whence it appears that he regards the com-
mon marine acid as furcharged with phlogif-
ton. M. Baume has therefore, from this
obfervation, the precedence in point of time
over Mr. Scheele, for the difcovery of the two
ftates of the marine acid; but he has not
defcribed the Angular properties of this acid,
when it is fuperfaturated with air, as the
celebrated Swedifh chemift has done.

The ufes of tin are very numerous. It
is applied to many purpofes in the arts, in
forming many veflels, organ pipes, deco-
rations, &c. Its amalgam is applied to
filver looking-glaffes. Copperfmiths pour
a mixture of tin and lead on copger veflels,
in the operation called tinning. Bell me-
tal, and bronze for ftatues, are compounds of
this metal, with copper. The pewterers
mix tin with bifmuth, regulus of antimony,
lead and copper, to make utenfils of all
forts, which are very little fubjedt to change
by expofure to air. Putty, or calx of tin,

is

TIN. 185

Is ufed in polifhing many hard bodies. Tin
is melted with calx of lead and fand, to
make enamel, as well as to glaze pottery, 6cc.
The cryftallized muriate of tin is ufeful in
the art of callico printing. Its folution in
aqua regia, heightens the tindture of cochi-
neal, of gum lac, &c. fo as to convert it
into the moft lively fire colour. The dyers
make ufe of this folution, which they call
compolition, to make fcarlet. When it is
mixed in the dyers bath, it forms a precipi-
tate, which carries down the colouring
matter, and depolits it on the fluff which
is to be dyed. This obfervation is due to
Macquer, whofe labours have greatly im-
proved this art.

The ufe of tin in culinary operations
has been efteemed very dangerous by fome
chemifts. Navier, in his treatife on coun-
ter poifons, &c. affirms, that ragouts, in
which tin fpoons have been left, as well
as fugar contained in a veffel of this metal,
have poifoned many perfons. Thefe un-
happy effe&s have been almoft generally at-
tributed to the arfenic which Geoffroy, in
the year 1738, affirmed to exift in tin, and
which Margraff imagined he had found in
the pureft tin, even in a very confiderable
proportion.

But the fears which have been excited
-on this fubjedt, are diffipated by the experi-
ments of Meffrs. Bayen and Charlard, whom

we

l86 TIN.

we have had already occafion to quote, in
the hiftory of this metal. Thefe chemifts
proved, by the moft decifive experiments,
i. That the quantity of arfenic, extracted
by Margraff, from the tin of Morlaix, and
which is near thirty-fix grains per half
ounce, would be much more than fufficient
to deprive this metal of all the foftnefs and
flexibility it is known to poffefs, and would
render it as brittle as zink. 2. That the
tin of Banca, and of Malacca, does not con-
tain an atom of this dangerous femi-metal.
3. That Englifli tin, in large blocks, affords
by the action of muriatic acid, a fmall quan-
tity of blackifh powder, often mixed with
copper and arfenic, in which the latter ne-
ver exceeds three quarters of a grain in the
ounce of tin, and is often lefs than that
quantity. 4. That the mixture made by
the pewterers, of the Englifh block tin,
with the pure tin of Malacca, or Banca,
diminifhes this dofe ftill more. 5. That
regulus of arfenic, united with tin, lofes a
part of its properties, and its corrolive action.
6. Laftly, That the fmall quantity of tin
thus alloyed, which may enter into food
by the daily ufe of veffels made of this me-
tal, is not fufficient to produce any effect
on the animal ceconomy, fince, according
to a calculation made on the lofs a tin plate
fuffered during two years wear, the quan-
tity fwallowed at moft does not amount

to

TIN. 187

to three grains in the month, and confe-
quently, the 5760th of a grain of regulus
of arfenicper day; fuppofing that tin wrought
at Paris, contained as much of this poifon-
ous femi-metal, as the plate or difh made
in London, on which Mr. Bayen made his
experiments.

We will here obferve, that the difagree-
ment between the Parifian chemifts and
Margraff, may arife from the latter having
made his experiments on Saxon tin, and the
former on the tin ufed in France, which
comes from the Eaft-Indies and from En£-
land.

We may alfo obferve, that manyphyficians,
who have directed their attention to metal-
lic fubftances, confidered as medicines, have
already acknowledged the innocence of this
metal, and have even advifed its filings to
be taken in fubftance, in diforders of the
liver, of the matrix, and for worms. Schulz,
in his differtation on the ufe of metallic vef-
fels, in the preparation of food and medicines,
recommends pure tin as very wholefome.
La Poterie prefcribes calx of tin as one of
the component parts of a preparation cal-
led antihecftic, which conlifts of a lixivium
of calx of the regulus of antimony and tin,
formed by detonation with nitre -, the al-
kali, which the water diliblves, always re-
tains a portion of the metallic calx.

Tin

1 88 LEAD.

Tin is recommended as a vermifuge. I
have been informed that is has been em-
ployed in large dofes at Edinburg, without
effedh Some country people are in the
habit of infufing fweet wine for four hours
in the cold, in a tin veffel, and giving a
glafs of this liquor to their children, who
are troubled with worms. Navier was a
witnefs to a girl of fixteen or feventeen years
old, who voided downwards thirty of the
worms called teres, with plentiful ftools,
fome hours after having taken a liquid of
this kind ; the medicine therefore ads as a
violent purgative.

CHAP. XVI.

Concerning Lead.

LEAD is an imperfect metal, of a dull
white, inclining to blue. The alche-
mifts give it the name of Saturn. It is the
leaft du&ile, the leaft elaftic, and the leaft
fonorous of all the metals ; it may be re-
duced into thin plates under the hammer,
and does not harden by beating. No me-
tallic fubftance has lefs tenacity. A wire
of lead of one tenth of an inch in diameter,
fupports no more than twenty-nine pounds
and a quarter, without breaking. It is the
third metallic fubftance in the order of

weight -x

LEAD. 189

weight ; a cubic foot of lead weighing 828
pounds, and it lofes in water between the
eleventh and twelfth of its weight. It is
very foft, and eafily cut with a knife ; has a
peculiar and remarkable fmell, which be-
comes ftronger by fridtion. Its tafte is fcarce-
ly fenfible in the mouth, but its effedt is very
manifeft in the ftomach and inteftines, whofe
nerves it irritates, producing pain, convul-
fions, ftupor, and palfy. It is fufceptible of
a regular form : the Abbe Mongez obtained
quadrangular pyramids, lying on their fides,
fo that of the four faces, one always is much
the largeft. Each pyramid is compofed as
it were of layers, or zones of other fmall py-
ramids, commonly terminating in one (in-
gle acute pyramid.

Lead is rarely found native ; Wallerius
and Linnaeus admit its existence in this ftate,
but it is denied by Cronftedt, Jufti, Mon-
net, &c. It is moft commonly in the ear-
thy, faline, or mineralized form, united
with fulphur, and forming galena. The
lead mines are commonly at confiderable
depths in the earth, and are fituated both
in mountains and in plains. Naturalifts
have diftinguifhed a great number of ores
of lead ; the moft eflential to be known are
the following.

1. Native calx of lead.- The fpathofe
ores of lead muft not be confounded with
this calx, which contains the cretaceous

acid.

I90 LEAD.

acid. It does not effervefce with the ni-
trous acid, and is commonly in white, grey,
ponderous folid maffes, or mixed with clay,
land, and chalk. The colour of the clay
accordingly, as it is more or lefs ferruginous,
conftitutes native mafficot and minium.
The native cerufe of lead is often found on
the furface of galenas.

2. Cretaceous lead, or the combination of
the calx of lead with the cretaceous acid j
this varies greatly in colour : it is white,
black, brown, yellow, or green, according
to the ftate of the iron which alters it. It
is in general called fparry lead ore, becaufe
it has the texture and cryftallization of cer-
tain fpars; it effervefces with the nitrous
acid, which difengages the cretaceous. The
following varieties of this fpecies are dif-
tinguifhed.

Varieties.

A. White fpathofe lead ore. This is a
calx pf lead, flowly depofited by wa-
ter, in a cryftallized form : it has
fometimes a femi-tranfparency, like
fpar; its cryftals are ufually hexa-
hedral prifms, truncated, or in cy-
lindrical ftriated columns, which ap-
pear to be compofed of agreat number
of threads, or in fmall fine needles.
It is fometimes found of a brilliant
white, like the filky gypfum. Other

fpecimens

LEAD. 191

fpecimens are of a yellowiih white.
Some of the priims are often fiftu-
lous. The white fpathoie lead ore,
abounds in Lower Britany, in the
mines of Huelgoet and Poullaouen.
Mr. Sage affirmed, that the white
lead ore is mineralized by the muria-
tic acid. Mr. Laborie afierted, that
it was a pure earth of lead, united
to fixed air, or cretaceous acid, and
cryftallized by water. The Aca-
demy of Paris, having caufed the ex-
periments of thefe two chemifts to
be repeated, adopted the opinion of
Mr. Laborie ; and Macquer has re-
lated the tranfa&ion in his Dictio-
nary, at the article Ores of lead.
The fpathofe lead ore is fometimes
found in the fame places as the gale-
na, and feems to be a decompofition
of that ore which has loft its ful-
phur, and whofe lead is in a calcin-
ed ftate; for it is not rare to find
galenas, which are paffing to the
ftate of white lead, as Mr. Rome de
Lifle has well obferved.
B. Some naturalifts have admitted a black
ore of lead. It is white lead altered
by an hepatic vapour, and by that
means is revived. It may be con-
fidered as a middle fpecies, between

white

192 LEAD.

white lead and galena, and is either
cryftallized, or in irregular mafles.

C. The green fpathofe lead. This mi-

neral is of a green, more or lefs
tranfparent ; often yellowifh, always
mixed with ochre and iron clay.
It is fometimes without any regular
form, and refembles a kind of mofs.
Such are moft of the fpecimens from
the mines of Hofsgrund, near Frey-
berg in Brifgaw. Green lead ore is
commonly cryftallized in hexahedral
prifms, truncated, or terminated by
hexahedral pyramids, either intire
or truncated near their bafe. It is
found in great plenty at St. Marie-
aux-Mines, and at Tfchoppau in
Saxony. It is proved that it owes
its green colour to the mixture of
iron, fince it is always found in
mines of that metal.

D. Spathofe lead ore of the colour
of peach bloflbms. Mr. Mongez
found this variety cryftallized like
white fpathofe lead, in the mines
of Huelgoet.

E. Yellow fpathofe lead ore. This va-

riety cryftallized in hexahedral tran-
fparent laminae, has not been known
till within a few years. The laminae
are from half a line, to four or five

lines

LEAD, I93

lines in diameter : they refemble glafs
of lead.

3. M. Monnet has difcovered lead com-
bined with the vitriolic acid. It is com-
monly in the form of a white mafs, foluble
in eighteen parts of water. Sometimes it is
blackifh, cryftallized in very long {trice, or
in friable ftala&ites : this laft variety efflo-
refces in the air, and becomes converted into
a true vitriol of lead. On account of this
effervefcence it is that M. Monnet calls it
pyritous ore of lead. Dr. Withering af-
firms, that there exifts in the Ifle of Angle-
fea, a large quantity of lead and iron mine-
ralized together by the vitriolic acid.

4. Lead appears to be combined with the
arfenical acid, in the red lead ore of Siberia,
of which Mr. Lehman firft gave a defcrip-
tion, in the year 1 766. This ore is of a very
beautiful red, and its powder refembles
carmine : it is often cryftallized in rhom-
boidal tetrahedral pyramids, fhort and ob-
liquely truncated. M. Mongez, who thinks
that arfenic exifts in its acid ftate, in all the
red ores of lead, has difcovered another ore
of a greenim yellow from Siberia, and con-
taining arfenic like the following.

5. M. Gahn difcovered the phofphoric
acid in a greenifh lead ore. There is likewife
a yellow and reddilh ore of this kind. If
this be diflblved in nitrous acid, and the
calx of lead precipitated by the vitriolic

Vol. III. N acid,

194 LEAD.

acid, the phofphoric acid may be obtained
by evaporation of the fupernatant liquor.
Meffrs. Metherie and Tenant have confirm-
ed the analyfis of M. Gahn, by experi-
ments made at Paris.

6. Lead is moft commonly found com-
bined with fulphur. This ore is, named ga-
lena ; it is likewife called alquifoux in com-
merce. It is compofed in general of la-
mina), which have nearly the colour and
afpedt of lead, but it is more brilliant, and
very brittle. A great number of varieties
of galena have been difcovered, viz.

Varieties.

A. Cubic galena. Its cubes, which are

of various fizes, are found either An-
gle or in groups ; it is often found
with the angles truncated, and is
common at Freyberg.

B. Galena in maffes. This has no re-

gular configuration ; it is very com-
mon at St. Marie.

C. Galena with large facets. It does not

feem to compofe regular cryftals ;
but it is intirely formed of large
laminae.

D. Galena with fmall facets. This ap-

pears to be formed like the mica, of
fmall, white, and very brilliant
fcales ; it is called white filver ore,
becaufe it contains a confiderable

quantity

LEAD. I95

quantity of that metal. The ore of
the mines of Pompean in Britany,
is of this kind.

E. Small grained galena ; fo called, be-

caufe it has a: very clofe grain. It
is likewife very rich in filver, and
is found with the foregoing ore.
Galenas in general contain iilver ;
none are known to be without it,
except that of Carinthia ; but it has
been obferved, that thofe galenas
afford the moff, whofe facets or
grains are the fmallefr. It feems as
if filver, being in fome mealure a
foreign fubftance in the combination
of galena, prevented the regular cry -
ftailizatiort of that ore.

F. Galena cryftallized like lead fpar, in

hexagonal prifms, or cylindrical- co-
lumns; it is found as well as the
foregoing, in the mines of Huelgoet
in Lower Britany. It contains lit-
tle filver, and feems to be merely
fpathofe lead mineralized, without
having loft its form. Cryftals of
pure fpathofe lead, intirely covered
wTith a very fine galena, are fome-*
times found in the fame piece, to-
gether with others which are abfo-
lutely changed into galena through-
out. M. Rome de Lifle pofTefTes
many fpecimens of this kind. I
N 2 have

196 LEAD.

I have in my collection a fpecimefi
of white lead ore, the bafe of whofe
prifms is abfolutely in the ftate of
galena; which proves the change we
are fpeaking of.
Galena is often found placed between two
layers of blackifh ochreous quartz, which
contain much filver, though the metal is
not apparent. M. De Dolomieu, the au-
thor of this obfervation, apprehends that
lead was originally mixed with the filver j
but that the water having carried off the
imperfect metal, left the fine metal in the
gangue. M. Monnet has difcovered, that
many galenas become vitriolized like py-
rites. He afHrms, that by warning one of
thefe, whofe furface was become white and
efflorefcent, he obtained a true vitriol of
lead.

7. Lead is fometimes naturally united
with fulphur, regulus of antimony, and fil-
ver. This ore, which is called antimo-
niated galena, is of a needled or ftriated
ftructure, like antimony. The femi-metal
is known by the white flowers which rife
during calcination. It is found at Salberg,
and at Saint Marie-aux-Mines.

8. There is another kind of galena, in
which the lead is united to fulphur, filver,
and iron. This martial galena is harder,
and more folid than the foregoing. It af-
fords

LEAD. 197

fords a yellow calx of lead during its fcori-
fication.

9. Laftly, calciform lead is often found,
together with galena, in fandy or calcareous
earths and ftones.

As almoft all the ores of lead, and efpe-
cially the galenas, contain a confiderable
quantity of filver, it is proper to make a
careful aflay of their contents. For this
purpofe, after having pounded and waflied
a certain quantity of the mixed ore, it is
roafted in a covered veflel, to prevent its
being fcattered by decrepitation. The ga-
lena does not lofe much <by the roafting.
After it has paffed this operation, it is
weighed, and melted with three times its
weight of black flux, and a fmall quantity
of decrepitated marine fait. The fixed al-
kali of the black flux, abforbs the fulphur j
the coal of the tartar, which is a part of the
fame flux, ferves to reduce a portion of the
metal which is in the calciform ftate; and the
marine fait oppofes the evaporation of part of
the matter contained in the crucible. After
the fufion, a button of lead is obtained, which
is to be carefully weighed, and then calcined
or vitrified, to feparate the lead from the fil-
ver it contains. But this aflay cannot be
greatly depended on, becaufe the alkali,
which is ufed as a flux, forms with the ful-
phur of the galena a liver of fulphur, which
N 3 diflblveb

I98 LEAD.

diflblves a portion of the lead. And it muft
alfo be confidered, that in the large way, a
reducing flux, foexpenfive as the black flux,
cannot be ufed. It is therefore more ad-
vifeable, to endeavour to melt the ore a-
mong the charcoal, in a reverberatory fur-
nace, or alone, with the addition of fome
cheap matter, to abforb the fqlphur, fuch
as a fmall quantity of iron, and glafs gall.

Bergman propofes to allay lead ores by
the nitrous acid. This acid diflblves lead,
and calcines iron, but does not affect ful-
phur. The folution is precipitated by the
cretaceous foda, and 132 grains of precipi-
tate reprefent 100 grains of lead in its me-
tallic ftate. If thefe ores contain filver, the
calx of this metal is feparated by the vola-
tile alkali, which diflblves it.

At Pompean, the lead ore which contains
filver is heaped up, warned with great care
on tables, and carried to the furnace, where
it is firft roafted by a gentle heat, and after-
wards melted by raifing the fire. The
melted lead is taken out of the furnace by
a hole which anfwers to one of the fides of
its hearth, and which had been clofed with
clay. The lead is then caft into pigs,
which contain filver. To feparate this pre-
cious metal, the lead is carried into another
furnace, whofe hearth is covered with afhes,
well warned, fifted, and rammed down. On
one of the fides of the hearth of this fur-

nacej

LEAD, I99

nace, are placed two large bellows, oppo-
fite to which are two gutters, which are
called the paffages of the litharge. When
the furnace is hot, the lead is calcined ; part
evaporates, and is fublimed in fmall chim-
nies which are over the paffages of the li-
tharge. Another portion of the metal is
abforbed by the bottom of the furnace; a
third part, which is the moft confiderable,
is calcined, and even partly vitrified ; this
is called litharge. The bellows drive it
out of the furnace, and likewife facilitate
the calcination and vitrification of the lead,
by the quantity of air they blow on the
furface of the metal in fufion. When the
litharge has been calcined by a moderate
fire, it is in the form of a red fcaly pow-
der, which is called litharge of gold, on
account of its colour. If the litharge has
been more heated, and is in a more vitri-
fied ftate, and of a pale colour, it is called
litharge of filver. Lallly, when the fur-
nace is heated ftrongly, lb as to melt the
litharge completely, and to fufe it in the
form of irregular flalaftites, it is called
frefh litharge. When the operation is
nniihed, the iilver contained in the lead re-
mains in the furnace. This filver requires
to be again refined, but in fmaller mafles,
in order that the remaining lead it ftill con-
tains may be feparated.

N 4 The

200 LEAD.

The lead which has been calcined in this
operation of tefting, is afterwards melted in
contadl with charcoal, and contains fcarcely
any filver : it is then caft into pigs, and ex-
pofed to fale. Spathofe lead melts, in con-
tadl with charcoal, in the fame manner as
the calces of lead.

Lead expofed to heat, melts long before
it becomes ignited. The heat neceffary to
hold it in fufion is fo inconfiderable, that
the hand may be plunged in it when melt-
ed without pain : and in this ftate it does not
burn vegetable fubftances. It is fcarcely
at all volatile, yet by a very ftrong heat it
fumes, and is reduced into vapours, like the
more fixed metals. If it be fuffered to cool
very flowly after being melted, and the
melted portion be poured off from that which
is become folid, it is found to be cryftalli-
zed in quadrangular pyramids, which we
have already defcribed.

Lead melted with the contact of air, foon
becomes covered with a grey and dull pel-
licle ; this pellicle is carefully taken off,
and reduced by agitation into a powder of
a greenifh grey, verging towards yellow.
When feparated by the iieve from the grains
of lead with which it is mixed, and after-
wards expofed to a more violent red heat, it
becomes of a deep yellow, and in this ftate is
named mafficot. This laft, flowly heated
by a gentle fire, afiumes a beautiful red co-

lour4

LEAD, 201

lour, and is known by the name of minium.
If maflicot be too ftrongly heated, it melts
into glafs without affording minium.

Lead by calcination becomes heavier, by
the quantity of about ten pounds in the
hundred. It was this increafe of weight,
produced in calcining lead, as well as the
neceffity of air for the operation, which
caufed John Rey, a phyfician of Perigord,
to fufpedr, that air is fixed in this metal
during the procefs. Dr. Prieftley has fince
confirmed the opinion of John Rey, by ob-
taining pure air from minium. The calx
of lead, though highly coloured, eafily
lofes this colour. If minium be heated ra-
ther too much, it becomes pale : if it more
ftrongly be urged by heat, it melts, with-
out addition, into a tranfparent glafs, fo fu-
fible, that it penetrates the crucible, and
efcapes. But if one part of fand be added
to three parts of calx of lead, the fand
jnelts by the afliftance of the calx, into a
beautiful amber coloured glafs. The colour
of this glafs is not fo deep, and refembles that
of the topaz, when two parts of the calx
of lead and one of fand, or pulverized flint,
are fufed together. A fimilar quantity of
the calx of lead added to common glafs,
does not alter its tranfparence, but gives it
a greater degree of weight, and more efpe-
cially a kind of uncluoufnefs, which renders
it capable of being cut and polifhed more

eafily

202 LEAD. '

eafily without breaking. This glafs is very
proper to form achromatic lenfes ; but it is
fubjecl: to veins, and to have a gelatinous af-
pedt. TheEnglifhcallitflintglafs; ourwork-
men find great difficulty in felecling pieces of
any confiderable magnitude, exempt from
ftriae, in that which is imported from England .
This great imperfection feems, in Macquer's
opinion, to depend on the principles of the
glafs not being uniformly combined : for
that purpofe it is required, that it Ihould
be long held in fufion ; but as the lead
would by that means be diffipated, the
flint glafs would lofe a part of its denfity
and unctuoufnefs, which are its chief merit.
Though all the phenomena of calcination
and vitrification of lead prove, that this
metal unites with great facility to the bafe
of pure air, it is neverthelefs one of thofe
metallic matters which adheres the leaft for-
cibly with that principle, fince it gives it out
by the fimple adtion of heat, as Dr. Prieftley
has fhewn. If minium be ftrongly heated
in a retort, vital air is obtained, and a por-
tion of the calx is reduced into lead. All
the calces, and even the glafles of lead, are
eafily decompofed by combuftible bodies.
For this purpofe it is fufficient to mix them
with charcoal, foot, greafe, oil, or rofin, or
in a word, any inflammable fubftance what-
ever, and to heat them for a certain time,
in order to obtain a button of lead. This

metal

LEAD, 203

metal has therefore lefs affinity with pure
air than many other metallic fubftances
have. Though it refembles tin in fome of
its properties, it is abfolutely oppofite to it
in its calcination and reduction. Tbefe phe-
nomena prove ftill more our explanation of
one of the caufes of the affinity of com-
pofition, viz. that the degree of affinity
of two bodies mutt not be eftimated by the
facility with which they combine, but by
the difficulty experienced in difuniting
them.

All the calces of lead, and efpeciallv mi-
nium, have the property of becoming charg-
ed with a certain quantity of cretaceous
acid, when expofed to air. If therefore it
be defired that a calx of lead ffiould remain
in a ftate of purity, it muft be kept de-
fended from the contact of air, or' ilightly
calcined before it is ufed, in order to fepa-
rate the cretaceous acid it may have ab-
forbed.

Lead expofed to air tarniihes the more
readily, accordingly as the air is damper.
It contracts a white ruft, which water car-
ries off by little and little. This white
powder is not a pure calx of lead, but is
combined with the cretaceous acid of the
atmofphere. The iilver extracted from old
lead, which has remained expofed for a
long time to the atmofphere, fhews that
the lead, which was not deprived of its iil-
ver

204 LEAD.

ver at the time it was firft ufed, has been parU
ly calcined by the action of the atmofpheric
air 3 fo that the filver which remained un-
altered, is gradually augmented by degrees,
in its proportion to the quantity of lead
deftroyed by the action of the atmofphere.

Lead is not altered by pure water, be-
caufe its principles are not Separated by that-
fluid : yet the internal parts of lead pipes
which conduct water, are covered with a
whitifh cruft, or a kind of cerufe, which
doubtlefs is produced by the action of the
different fubitances contained in the water
on this metallic fubftance.

Lead does not unite with earthy matters,
but in its calciform ftate.

The action of the falino-terreftrial fub-
itances, and cauftic alkalies on lead, or its
calces, are not known.

This metal is foluble in all the acids, but
oil of vitriol does not attack it, except it be
boiling, and the lead be in fmall pieces.
In this procefs volatile fulphureous fpirit
and gas pafs over. When moft of the
acid is decompofed, the mixture is white
and dry, and feparates into two portions,
on being warned with diftilled water. The
moft confiderable part is infoluble in
water, and is a calx of lead formed by
the bafe of the air, which the metal
has feizcd from the oil of vitriol during
the time of the difengagement of the ful-
phureous gas. This calx may be melted

or

LEAD. 205*

or reduced like that which is made by the
combined a&ion of fire and air : the por-
tion diffolved by the water, is a combina-
tion of vitriolic acid and calx of lead.
This folution, by evaporation, affords fome
needles of vitriol of lead. Meffrs. Baume
and Bucquet have not fpoken of this fait,
but under that form. M. Monnet fome-
times obtained it in prifmatic fhort columns.
M. Sage blames this chemift, becaufe he
affirms that he found vitriol of lead to afford
cryflals in tetrahedral prifms. It is a very
cauflic fait, and requires at leaft eighteen
parts of water to diffolve it. It is decom-
pofed by fire alone, and alfo by lime and
alkalies.

The nitrous acid appears to adt very
ftrongly on lead. When this acid is well
concentrated, the lead is quickly reduced
into a white calx, by means of the oxygi-
nous principle which is feparated from the
nitrous acid, at the fame time that the ni-
trous gas is difengaged; but if the acid be
more feeble, it is lefs decompofed, and a
fufficient quantity remains to diffolve the
calx of lead. During this folution a grey
powder is precipitated, which Groffe took
to be mercury; but M. Baume affirms,
that this matter is nothing but a portion of
the calx of lead ; and I have feveral times
in vain attempted to obtain mercury by
fublimation, and by urging this powder

with

%o6 LEAD.

with a fire capable of reducing mercury, if
it had been in the ftate of calx. This fo-
lution does not afford a precipitate on the
addition of water. Its cryftals obtained by
cooling, are of an opake white, in the form
of flat triangles, whofe angles are truncated.
The fame folution, by a flow evaporation
of feveral months, afforded cryftals, the
largeft of which was one inch in thicknefs,
of the form of hexahedral pyramids, whofe
three faces are alternately large and fmall,
and whofe point is truncated, fo that each
cryftal is an eight fided folid. Rouelle has-
defcribed this fait very well. The nitre of
lead decrepitates in the fire, and melts with
a yellowifh flame when laid on an ignited
charcoal. The calx, which is at firft yel-
low, becomes quickly reduced into glo-
bules of lead. This fait is decompofable by
lime and alkalies. The vitriolic acid, though
it a£ts but feebly on lead, has neverthelefs a
ftronger affinity to that metal than the ni-
trous acid. If pure vitriolic acid, or any
neutral, earthy, or alkaline vitriolic fait be
added to a nitrous folution of lead, a white
precipitate is formed in a very fhort time :
this precipitation takes place, becaufe the
vitriolic acid feizing the calx of lead, forms
with it vitriol of lead, fimilar to that which
is prepared by the immediate combination
of the vitriolic acid with that metal.

The

LEAD. 207'

The pure muriatic acid, by the affiftance
of heat, calcines lead, and diffolves part
of its calx; but it is difficult to iaturate it
completely. This lblution always has an
excefs of acid, but neverthelefs affords, by
a ftrong evaporation, cryftals in the form of
fine and brilliant needles, as M. Monnet
has obferved. The muriate of lead is fcarce-
ly at all deliquefcent. Lime and alkalies
decompofe it like the vitriol of lead. This
metal becomes more readily and intimately
combined with the muriatic acid, by adding
the acid itfelf, or the acid united with an
alkaline or earthy bale, to a folution of
nitre of lead. A white precipitate is im-
mediately formed, which is much more
abundant than that produced by the vitrio-
lic acid, and refembles a coagulum. It is
a combination of the calx of lead with the
muriatic acid, which has feparated the metal
from the nitre. This fait falls down, be-
caufe it is much lefs foluble in water than
nitre of lead ; if it be expofed to heat, it
gives out vapours, whole tafle refembles
fugar, and melts into a brown mafs, called
corneous lead, becaufe it partly refembles
the filver which is diftinguilhed by the
fame name; it is foluble in thirty times its
weight of boiling water. The lblution of
this fait, by evaporation, cryftallizes into
fmall, fine, and brilliant needles, which
form bundles, or unite by one of their ex-
tremities

208 LEAD,

tremities in an obtufe angle. Mr. Sage
affirms, that this folution affords, by infen-
fible evaporation, cryftals in ftriated hexahe-
dral prifms. The folution of corneous lead
is decompofable by the vitriolic acid, which
occafions a precipitate refembling that be-
fore obtained from the folution of nitrous
acid. This difcovery, due to GroiTe, has
been verified by Baume ; it detects an er-
ror in the eighth column of the table of
affinities of GeofFroy, which afferts, that
lead has a flronger affinity with the muria-
tic acid than with the other mineral acid.

All the folutions of lead are precipitated
of a black or brown colour by liver of ful-
phur ; a kind of galena being formed by the
transition of the iulphur to the calx of lead,
which feems to mew that lead is in the cal-
ciform ftate in that ore. In thefe experi-
ments a double decompofition takes place,
without a double elective attraction, becaufe
the faline bafe of the hepar would decom-
pofe the vitriol, the nitre, and the muriate
of lead, without any other addition.

All the calces of lead are foluble in acids
as readily as lead itfelf, and often with
greater facility. Minium lofes its colour
in thefe folutions. Lead does not act on
the vitriolic neutral falts, neither does it
decompofe vitriolated tartar by heat, as tin,
zink, and regulus of antimony do.

Lead does not fenfibly detonate with
nitre. When this neutral fait in powder

is

LEAD. 209

is thrown on the melted metal in a low red
heat, it excites fcarcely any commotion or
apparent flame, though the lead is calcined
and vitrified by the alkali of nitre, and takes
the form of fmall yellowifh fcales, fimilar
to litharge.

Lead decompofes fal-ammoniac very well
by the affiftance of heat. This property is
common to many of the metals. The calces
of lead triturated with this fait, difengage
the alkaline gas in the cold ; but if the
mixture be heated in a retort, the decompo-
fition is very rapid, and a volatile, cauftic,
and very penetrating alkaline fpirit comes
over. Some chemifts have affirmed, that
the volatile alkali obtained by minium, e'f-
fervefces with acids, and have thence con-
cluded, that minium contains cretaceous
acid. But Bucquet has obferved, that this
effervefcence is produced by a portion of
alkaline gas, volatilized by the heat produced
during the combination of the alkali and
the acid, and that it only takes place when
concentrated acids are ufed. He has made
very ingenious and decifive experiments on
this fubjedt. After having introduced into a
glafs vellel over mercury, volatile alkaline
fpirit, obtained by means of minium, he
added a fufficient quantity of vitriolic acid,
fomewhat concentrated, for the faturation
of the alkali. The ebullition, or difen-
gagement of gas, was immediately excited,

Vol. III. O which

210 LEAD.

which was quickly after abforbed, and con-
firmed of alkaline gas. The mafs which re-
mains in the retort after the decompofi-
tion of fal-ammoniac by minium, is mu-
riate of lead, which melts by a moderate
heat into corneous lead, and is totally fo-
luble in water. This mafs was employed
by MargrafF, in the procefs for making the
phofphorus of urine.

Inflammable gas very fenfibly afFedts lead,
by producing changeable colours of the
rainbow on its furface, and revivifying its
calces. Minium, in contact with this gas,
becomes black, and of a leaden colour. Dr.
Prieflly has obferved, that a tube of glafs,
containing inflammable gas, fealed her-
metically, and expofed feveral days to the
heat of a fand bath, was intirely covered on
its inner furface with a black tinge, and
that a vacuum, with drops of water, was
formed in the tube. This valuable expe-
riment is explained by the greater affinity
which the inflammable principle has to the
oxyginous principle, or bafe of air, than
lead has; and this is likewife proved by the
total incapacity of that metal to decompofe
water. Englifh glafs contains a large pro-
portion of calx of lead. The inflammable
gas acted on this calx, and by degrees de-
prived it of its oxyginous principle, with
which it formed drops of water ; the lead

• at

LEAD. 211

at the fame time affuming the metallic
colour.

Sulphur readily unites with this metal.
When thefe two fubftances are melted
together, a brittle compound is produced,
of a plated texture, and a deep grey brilliant
colour. This matter, which nearly refem-
bles galena, is much more difficult to melt
than lead ; a phenomenon peculiar to the
combinations of certain metals with fulphur.
Thofe which are very fufible, become more
difficult of fufion when united to that fub-
ftance, while fuch as are difficultly fufed,
acquire a great degree of fufibility by this
addition.

The alloy of lead with arfenic has not been
examined. Nickel, manganefe, cobalt, and
zink, do not unite with lead by fufion ;
regulus of antimony forms a brittle alloy
with fome brilliant facets, fimilar in texture
and colour to iron or fteel, according to the
proportions of the mixture, and of a fpecific
gravity, more coniiderable than the two
metallic fubftances, feparately taken, would
compofe.

Lead combines with bifmuth, and affords
a metal of a fine and clofe grain, which is
very brittle. Mercury diffolves lead with
the greateft facility ; this amalgam is made,
by pouring hot mercury into melted lead.
It is white and brilliant, and becomes folid
at the end of a certain time. When tritu-
O 2 rated

2J2 LEAD.

rated with the amalgam of bifmuth, it be-
comes as fluid as running mercury. It is
proper to obferve, that this Angular pheno-
menon takes place in the union of three
very fufible ponderous, and more or lefs vo-
latile, metallic matters.

Lead unites very eafily by fufion with
tin. Two parts of lead and one of tin,
form an alloy more fufible than either of
the metals taken feparately, and constitutes
the folder of the plumbers. Eight parts
of bifmuth, five of lead, and three of tin,
compofe an alloy fo fufible, that the heat of
boiling water is fufficient to melt it, as Mr.
Darcet has difcovered.

The alloy of lead with tin being employ-
ed frequently in economical ufes, and the
firft of thefe metals being capable of ren-
dering utenlils made with the fecond very
dangerous for culinary or pharmaceutical
purpofes, it is an inquiry of confiderable
importance, to afcertain the proportion of
lead, which very often amounts to more
than the public regulations permit. Meffrs.
Bayen and Charlard have defcribed an excel-
lent procefs for determining the quantity
of this vile and dangerous metal contained
in pewter, or other compounds of tin.
It confifts in diflblving two ounces of the
fufpecled metal, in five ounces of a good
pure nitrous acid. The calx of tin is to be

wafhed

LEAD. 213

warned with four pounds of diftilled water,
and dried, and the water evaporated by the
heat of a water bath. By this evaporation
nitre of lead is afforded ; which being cal-
cined, the weight of the refidue mews the
quantity of that metal contained in the tin,
allowing a few grains for the augmentation
of weight arifing from calcination, as well
as the other metallic fubftances, fuch as zink
and copper, which the tin under examina-
tion may contain. Thefe chemifts, by this
method afcertained, that fine wrought tin or
pewter contains about ten pounds of lead in
the hundred, and that the common tin, fold
in France under that name, often contains
twenty-five pounds in the fame quantity; an
enormous dofe, furhcient to expofe thofe who
ufe veffels made of this compoiition to the
greateil danger. Lead is almoft conftantly
a part of the veffels continually ufed, fuch
as meafures for diftributing fluids, more
efpecially wine. It fcarcely need be ob-
ferved, that a liquid, which quickly becomes
acid, may unite with lead, and may convey
into the vifcera of thofe unfortunate perfons
who drink it, the feeds of diforders fo much
the more dangerous, as their caufe is not
fufpected.

The pewterers have feveral methods of

difcovering the finenefs of tin, and the

quantity of lead it contains : fimple infpec-

tion often anfwers their purpofe -, and the

O 3 weight

214 LEAD.

weight and the noife produced in bending,
greatly affifts their judgment. They have
two kinds of affay: the one called affay by
the ftone, which confifts in pouring the
melted tin into an hemifpheric cavity, hol-
lowed in a thunder ftone, terminated by a
channel. The phenomena which the tin
exhibits in its cooling, its colour, the
roundnefs of its furface, the depreffion of
its middle part, the noife which the tail of
the affay bent backwards and forwards pro-
duces, are the chief figns which the intel-
ligent workman takes notice of, and by long
obfervation applies with confiderable accu-
racy, to afcertain the finenefs of the metal.
But this affay ufed by the mafter pewterers
at Paris, does not appear to be fo exadt as
the other praftifed by the mafters in the
country, though reje&ed with difdain by
the former. This fecond affay is called by
the ball or medal, becaufe it confifts in
pouring the tin intended to be affayed, into
a mould, which gives it the form of a ball,
or a flat mafs fimilar to a medal. The
weight of this fample is compared with a
fimilar volume of fine tin poured into the
fame mould ; the more the tin under exa-
mination exceeds that of the fpecimen in
weight, the more it is alloyed with lead.
Meffrs. Bayen and Charlard with great rea-
fon prefer this laft affay, the principles of
which are more certain, than the circum-

ftances

LEAD. 215

fiances on which the workman, who ufes the
affay of the ftone, muft ground his judg-
ment.

Lead is ufed in a great number of .works.
It forms a part of many alloys, and is made
into pipes for the conveyance of water.
Its calces are employed in glafs-making, and
in the preparation of enamels. It is ufed
to imitate the colour of yellow precious
ftones, and to give fufibility to the glaze
of earthen ware. Uteniils and veffels pro-
per for economical ufes are made with this
metal, but not without danger in their ufe,
as we have before obferved. Fountains, or
veflels of lead, in which water is fuftered
to remain a long time, often communicate
a noxious quality to it. Its vapour is dan-
gerous to the workmen who melt it, and
its tafte is ilill more dangerous to fuch as
file and fcrape it. This metal, lodged in
certain parts of the ftomach and inteftines,
produces violent cholics, often accompani-
ed with vomiting a very brown bile, and
characterized by the flatnefs of the belly,
and linking of the navel, It has been ob-
ferved, that in fuch cafes, antimonial eme-
tics and purges have been attended with
great fuccefs. Navier advifes the different
livers of fulphur, in cafes of poifoning by
the preparations of lead, as well as in fuch
as are produced of arfenic and corrofive fub-
limatej and it is more particularly in the
O 4 palfy

2l6 LEAD.

palfy and tremblings, which commonly re*
main after the painters cholic, that this
phyfician boafts of the good effects of liver
of fulphur and hepatic waters, At all events,
when thefe fafts are duly confidered, we
ought to avoid the internal ufe of pre-
parations of lead, and only apply it as aa
.external medicine ; and even in this laft
cafe, it ought not to be adminiftered, but
with all that care and caution which are re-
quired in the ufe of a ftrong repellent.

CHAP. XVII.
Concerning Iron.

TRON, called Mars by the alchemifts, is
■*• an imperfedt metal, of a white livid co-.
lour, inclining to grey, internally compofed
of fmall facets. It is fufceptible of a very
beautiful and brilliant polifh, and its hard-
nefs and elafticity are fuch, that it is capa-
ble of deflroying the aggregation of all the
other metals.

Iron has a confiderable fmell, efpecially
when rubbed or heated. It likewife has a
very evident ftyptic tafte, which acfts flrong-
ly on the animal economy. Next after
tin, it is the lighted of metallic fubftances ;
a cubical foot of this metal, when forged,
weighs 580 pounds. It may be extended into

plates

-IRON. 217

plates by beating, but as it is very hard, and
becomes ftill harder under the hammer, it
cannot be made into leaves. Its ductility,
when drawn into wire, is much more con-
fiderablej very line wires being made of this
fubftance for mufical purpofes : this pro-
perty appears to depend on its tenacity.
In fact, iron is the moft tenacious of all
metals, except gold. An iron wire of one
tenth of an inch in diameter, fuftains a
weight of 450 pounds without breaking.

Pure iron has a peculiar cryftalline form.
In the furnaces, where the metal has been
fuffered to cool flowly, quadrangular, arti-
culated, and branching prifms, formed of
octahedrons, implanted one in the other,
were found. This obfervation was made
by Mr. Grignon, mafter of the forges at
Bayard, in Champagne. Laftly, befides all
the properties which iron partakes in com-
mon with every other metallic fubftance, it
prefents three which are peculiar to itfelf.
The firft is magnetifm, or the property of
being attracted by the magnet, and of itfelf
becoming a very good magnet, either by
remaining a long time in an erect pofition,
or in the direction from fouth to north ; or
by ferving as the conductor to the electric
fire of thunder, as many facts attefl * or by
being ftrongly rubbed againft another piece
of iron. The fecond property is that of
taking fire, or fuddenly melting by the ftroke

of

2l8 IRON.

of a flint; a phenomenon to which the poets
univerfally attribute the difcovery of fire by
the firft men. The third property which
diftinguifhes it, is, that it is the only me-
tallic fubftance which is found in plants
and animals, whofe fluids it partly colours.
It is likewife probable, that thefe organic
beings themfelves form this metal : for
fuch plants as grow in pure water, contain,
iron, which may be extracted from their
alhes.

Iron is a metal which is very abundant
in nature; fince, independent of that which
plants and animals contain, it is found in
almoft all coloured ftones, bitumens, and
in almofl all metallic ores. But we fhall,
in this place, attend only to the mineral
fubftances which contain it in fuch large
quantities, as to be worth extracting.
In thefe ores, which are very numerous,
iron is either in the metallic or calciform
ftate, or elfe mineralized by different fub-
ftances.

i. Native iron is known by its colour
and malleability. It is very rare, and is
only found occafionally in iron mines. Mar-
grafF found it in a fibrous form at Eiben-
ftock in Saxony. D. Pallas difcovered in
Siberia, a mafs of 1600 pounds; and Mr.
Adanfon affirms, that it is common at Sene-
gal. Some naturalifts think, that thefe na-
tive fpecimens of iron are produced by art,

and

IRON. 219

and have been buried in the earth by acci-
dents.

2. Iron exifts very often, more or lefs
calcined, in the form of ruft. It is diftin-
guifhed into rich and poor, fufible and
refradlory iron. The rich iron is not much
rufted, and contains only a very fmall quan-
tity of earth. Fufible iron is that which
melts eafily, and affords caft iron of a good
quality. The metal is united in its ore to
feveral fufible ftones. Dry or refractory
iron is calcined, and mixed with infufible
. fubftances. All the bog ores cf iron are
commonly difpofed in beds, in the manner
of ftones, and feem to have been depofited
by waters. It is very often in the form
of fpherical bodies, either flat or irre-
gular. Organic matters, fuch as wood,
leaves, bark, fhells, &c. are not unfrequent-
ly found in the ftate of bog ores. This
kind of converfion or tranfition, feems to in-
dicate a fort of analogy between this metal
and organic fubftances. In the wood of
Bologne, near Autueil, there is a mine of
bog ore of iron, in which vegetable fub-
ftances become mineralized, almoft imme-
diately under our eyes.

3. The eagle ftones, or aetites, is a variety
of the bog ore ; they are bodies of differ-
ent forms, commonly oval or polygynous,
compofed of concentric layers, difpofed
round a nucleus, which is frequently move-
able

220 IRON.

able in the centre of the ftone. The dry-
ing and fhrinking of thefe layers, forms a
middle cavity, in which feveral fragments,
more or lefs considerable, exift loofe, or
detached. This ftone has received the name
it bears, becaufe it was formerly thought
that the eagles depofit it in their neft, and
that it has the property of facilitating births.
Hence it has been concluded, that this ftone
afts ftrongly on the foetus in utero. Some
authors have even affirmed, that it was
poffible to accelerate the labour of women,
by tying the eagle ftone to their leg, or to
retard it by tying it to their arm.

4. The hematites are a fort of muddy iron
ore, which feem to be formed in the man-
ner of ftala&ites j its name comes from its
colour, which is commonly red, or of a
blood colour, though this colour is fubjedt
to variations. -The hematitis is ufually
compofed of layers which cover each othera
and are themfelves formed of convergent
needles; the external part of this ore is
covered with tubicles ; it is not only
diftinguifhed by the colour, but by the
form. Such are the hematites in needles
found in Lorrain j the tuberclated hema-
tites are in the form of bunches of grapes,
or the hematites botrytes, &g. Thefe ores
are often found together with the muddy
iron ore, and are depofited on a variety of
different bodies.

5- The

IRON". 221

5. The loadftone is a muddy iron ore,
which fome perfons however imagine to be
very near the metallic ftate. It is known
by its property of attracting fteel filings,
and is found in Auvergne, and in Bifcay in
Spain ; the varieties are diftinguifhed by
their colours.

6. Emery, fmyris, is a grey or reddifti
iron ore, which feveral mineralogifts confi-
der as a fort of hematites ; it is very hard,
is very refractory, and is abundantly found
in the ifland of Jerfey and Guernfey. It
is reduced into powder, in mills, and in this
ftate is ufed to polifh glafs and metals.

7. Spathofe iron ore, is a calx of iron
combined with the cretaceous acid, and
worn by water; it is ufually of a white
colour, though all the fhades of grey, yel-
low, and red, are found. It is always dif-
pofed in laminae of different thicknefs, femi-
tranfparent like fpar; is heavy, and often
regularly cryftallized. Confiderable quar-
ries of this ore, frequently mixed with py-
rites, are wrought; as that of Allevard in
Dauphiny. Sometimes it is mixed with
grey filver ore, as the iron of Baigorry ; or
with manganefe, as that of Styria. Some
mineralogifts think, that it is a fpar in
which the metallic calx has been depofit-
ed. Spathofe iron ore is decompofed with-
out addition, in clofe veflels, and affords
cretaceous acid; the iron remaining in a

black

222 IRON*

black powder, is ftrongly attracted by the?
magnet, and eafily melts by the adtion of &
confiderable heat.

8. Nature likewife prefents iron in the
faline ftate, united to the vitriolic acid, and
forming martial vitriol, or green copperas.
This vitriol is found in the galleries of iron
mines, efpecially thofe that contain pyrites;
it is fometimes found in green cryftals, or
in the form of fine ftaladtites ; and at other
times it is not fo pure. When it has loft
the water of its crystallization, it is of a
white or greenifh colour ; if it has fuffered
a calcination rather ftrong, it is yellow ; and
if the calcination be carried on ftill farther,
a confiderable portion of acid of vitriol will
be obtained, and it is called natural colcothar,
or chalcites. If mixed with certain inflam-
mable matters, this fait is called melantari,
on account of its black colour; all thefe
different matters have received the name of
lapides atramentarii, becaufe like the vitriol
of iron, they are proper to make ink.

9. Iron is often found united to fulphur,
and then conftitutes martial pyrites. This
kind of ore has received the name of py-
rites,, becaufe it is fufficiently hard to give
numerous fparks when flruck with the fteel.
The martial pyrites are commonly in fmall
red mafies, fometimes regularly formed;
they are ufually fpherical, cubical, or dode-
cahedral, but their form varies confidera-

bly,

IRON. 223

bly> as may be feen by confulting the Pyri-
tologia of Henckel. Some are brown on
the outfide, and of the colour of iron ;
others are yellowifh, and confiderably re-
fembling copper ores, even at their furface.
All are yellow, and as it were coppery,
within, and for the moft part are compofed
of needles, or pyramids of fcveral fides,
whofe fummits converge towards a common
centre. The pyrites are commonly dif-
perfed, and particularly in copper mines,
in the neighbourhood of iron mines and in
clays, and coal mines. The upper ftratum
of the latter is almoft always pyritous. All
the feveral kinds of pyrites are eafily de-
compofed. A flight degree of heat is fuf-
ficient to deprive them of their fulphur.
They are almoft always fpontaneoufly chan-
ged, when expofed to the air, efpecially in
a moift place. They fwell, burft, lofe their
brilliancy, and become covered with an
efflorefcence of a greenifh white, which is
martial vitriol. It feems that this altera-*
tion, which is called vitriolization of the
pyrites, depends on the united action of air
and water on the fulphur. Vitriolic acid
is thus formed, which diflblves the iron,
and rifes above the furface of the pyrites
like a kind of vegetation, which gradually
feparates the fmall pyramids which compofe
this mineral. All pyrites do not efflorefce
with the fame facility. The globular py-
rites, whofe colour is very pale, and texture

clofe,

224 IRON.

clofe, become vitriolized very quickly.
The others, which are of a brilliant yellow,
or of the colour of copper, and are formed
of fmall laminae, very evenly applied on
each other, do not efflorefce but with great
difficulty, and muft be very carefully dis-
tinguished from the foregoing, becaufe they
differ from them in colour and texture,
and other properties.

jo. Iron is found combined with arfenic,
both being in the metallic ftate. This ore,
which is the true mifpickel, is white, bril-
liant, granulated, or in facets, and does not
contain fulphur, as the arfenical pyrites,
properly fo called, does. Wolfram was for-
merly confidered as an arfenical iron ore,
but it is now known to be an ore of Tung-
ften.

ii. Black iron ore is known by its co-
lour, by its property of being more or lefs
attracted by the loadftone, and by being not
at all foluble in acids. This iron is fometimes
cryftallized in the form of polyhedrons, or
in rounded lamina?, and prefents different
fpots of very brilliant rainbow colours : fuch
is that of the Ifland of Elba. This iron
forms a very confiderable mountain, from
which it is dug at the furface. The Swe-
dish iron ore is likewife black, but is not
cryftallized. It is in maffes more or lefs
folid, mixed with quartz, fpar, afbeflos, &c.
it is often hard enough to take a polifh, at

its

IRON, 225

its furface appears as it were compofed of
fpeculae, for which reafon it, as well as the
preceding, is called fpecular iron ore. It
is found united in quarries of very confide-
rable extent. This ore varies in its colour;
when it is perfectly black, it is ftrongly
attracted by the magnet ; the blueifh is lefs
attracted, and the grey fcarcely at all. The
iron of Norway is likewife black, but it is
commonly in fmall fcales, like mica, often
mixed with garnet and fchorl. Black iron
ore has fometimes the form of grains. It
is likewife cryftallized in calces, which has
caufed it to be denominated by fome natu-
ralifts, galena of iron, or eifen-glants. When
the micaceous ore of iron is black, it is
called eifen-man, efpecially if the fcales be
very large. When they are red, and the
powder which covers them is of the fame
colour, it has the name of eifen-ram. Iron ore
in very regular, black octahedral cryftals,
and difperfed on a kind of fhiftus, or hard
fteatites, which comes from Sweden, Cor-
fica, &c. appears to belong to this clafs.
It is attracted by the magnet, and is very
brittle.

Though the different kinds, of iron ore,
confidered in this article, feem to have a
flrong analogy with each other; feveral mi-
neralogifts have confidered them as very
different, and have arranged them accord-
ingly. This variety of opinions arifes from
Vol. III. P the

226 IRON.

the exadt knowledge of their nature not
being yet obtained. It feems, that among
thofe ores, there are fome more or lefs ap-
proaching to the metallic ftate, as the octa-
hedral iron ore of Cornea, and of Sweden,
which M. Mongez compares to the mar-
tial .^Ethiops. This is ftrongly attracted by
the magnet. Others, on the contrary, ap-
proach more to the ftate of calx, as the iron
of the Ifle of Elba, and efpecially the eifen-
man, and eifenram, which are not afted on
by the magnet.

12. Iron is fometimes found in the form
of a blue powder, of a more or lefs deep
colour. In this ftate it is called native Pruf-
iian blue. It is mixed wTith vegetable
earths, and efpecially with turf.

13. It has been discovered fome years ago,
that iron is often naturally united with an
animal acid, known by the name of the phof-
phoric acid. The muddy or bog ores are
fometimes of this nature; a portion of this
compound remaining in the iron, gives it
the property of being brittle when cold.
Bergman, who was acquainted with this
ftate of iron, without having determined its
nature, called it fideritej feveral other che-
mifts have fince called it water iron. We
fhall hereafter explain the method of fepa-
rating this fait of cold fliort iron.

14. Laftly, Iron being the moft abundant
of all the metals, is frequently found mixed

with

IRON. 127

with fand, clay, chalk, and is the colouring
matter of a great number of different earths
and ftones.

Iron ores are afTayed after the following
manner, by the dry way. After reducing
them into powder, they are mixed with
double their weight of pounded glafs, one
part of calcined borax, and a fmall quan-
tity of charcoal in powder ; the mixture is
exactly triturated, and put into a crucible;
a fmall quantity of marine fait is added,
the crucible is then covered, and the heat
raifed to melting. When the mafs is very
flowly cooled, iron, more or lefs malleable,
and in a fmall fpherical button, often cry-
ftallized at its furface, is found.

Bergman propofes to arTay iron ores by
the humid way. He ufed the muriatic acid
to diffolve the iron, and precipitated it by
a portion of alkali. If other matters were
mixed with the iron, he calcined them, and
feparated them by the nitrous and acetous
acids, and afterwards diffolved the iron by
the muriatic acid.

The treatment of iron ores varies, accord-
ing to the ftate in which the metal is found.
There are fome ores which require no pre-
paration before the fmelting ; others require
to be pounded and wafhed, and fome to be
roafted, in order that they may become
more friable and fufible.

P 2 The

228 IRON.

The bog ores and fpathofe iron ore, arc
examined in the fame manner, by fmelting-
them with charcoal. The furnaces in which
iron is melted, are of various heights, from
twelve to fifteen feet ; their cavity repre-
fents two quadrilateral pyramids, which join
at their bafe about the middle of the height
of the furnace. At the bottom of the fur-
nace an aperture is made, from which the
melted metal is to flow out; this aperture,
which is clofed with earth, correfponds with
a triangular cavity, hollowed in fand, and
intended to receive the melted iron. The
procefs is begun by throwing fome lighted
brufhwood into the furnace, and afterwards
charcoal, with the ore, and certain fluxing
matters % thefe are commonly of calcareous
flone, with certain argillaceous (tones, and
fometimes quartz and flints. The flones,
the charcoal, and the ore, are alternately-
thrown into the furnace, obferving to cover
the whole with a bed of charcoal, which
mufl rife to the upper opening of the fur-
nace. The fmelting is performed by the
help of two flxong pair of bellows ; and the
iron melts paffing through the charcoal,
which reduces it. The ftony matters ad-
ded to the ore, becoming melted and vi-
trified, facilitate the fufion of the iron,
which begins at the narroweft part of the
furnace. The melted metal is collected at

the

IRON. 229

the bottom, and by opening the anterior
aperture of the furnace, it is fuffered to
run out into the cavity in the fand; it is
then called crude iron. A vitreous mat-
ter called flag, paffes after the iron, and
confifts of the ftones added to facilitate the
fufion. Its colour is green, whitifh, or
blue, which it receives from a portion of
the calx of the iron. The metal, thus
obtained, has not the leaft ductility. Me-
tallurgifts are not agreed concerning the
caufe of this property of caft iron. Some
think that it is owing to a portion of the
vitreous matter; others attribute it to part
of the calx of iron not being reduced.
Brandt fuppofed it toarife from arfenic, and
Mr. Sage thinks that it is produced by
zink. Eucquet confidered caft iron as iron
not well reduced, and ftill containing a por-
tion of metallic calx interpofed between its
parts. Bergman, who made many experi-
ments on iron, has proved, that the brittle-
nefs of caft iron depends on a certain quan-
tity of foreign matter, which he fuppofed to
be a peculiar fubftance, and called fiderite.
It has been lince difcovered, that fiderite is
a compound of iron and phofphoric acid,
and that it is likewife found in fome kinds
of malleable iron, as we fhall hereafter fhew.
Metallurgifts diftinguifh feveral kinds of
caft iron, white, grey, black, &c. That
P 3 which

23O IRON,

which is of a grey brown, with blackifh
fpots, is called fpeckled iron. The white
caft iron is of the worft quality, and ap-
proaches to the chara&er of femi-metals ;
the grey is of an intermediate quality be-
tween the firft j and the black is the heft,
and affords iron of a good quality.

The caft iron is carried to be refined in a
forge furnace, with a hearth rather hollow,
in which a mafs of caft iron, covered with
aconfiderable quantity of charcoal, is placed,
and the fire is urged by bellows, till the iron
begins to foften. When it is in this ftate,
it is repeatedly ftirred, in order that it may
prefent a larger furface, that the portion of
iron which is in the ftate of calx may be
reduced. The metal by this operation is
likewife deprived of a portion of fiderite
which remained in it. It is next carried to
the hammer, to be wrought into the form
of bars. The hammering, by bringing the
parts of iron nearer together, facilitates the
feparation of the fiderite, and the portion of
calx which the metal ftill contained, and
by that means completes what was left de-
fective by the fufion. This heating and
hammering is repeated a number of times,
till the iron has acquired the delired degree
of perfection.

Two kinds of forged iron are diftinguifhed;
foft iron and fteel. Steel is the beft, the hard-
eft, thefineftj and the clofeft grained iron . Soft

iron

IRON. . 23I

iron approaches to fteel in its qualities ; its
grain however is not fo clofe, and when it
is broken by bending backwards and for-
wards, it draws out, and appears to be com-
pofed of fibres. This fibre, or nerve, how-
ever, is only produced by the manner of
breaking, and does not appear at all when
the foftefl iron is broken fhort and fuddenly;
at the fame time that iron of the worfl qua-
lity will appear fibrous, if it be broken flow-
ly and cautioufly. The quality of iron may
be eflimated much better from its grain
than from its fibres. Brittle iron has a large
grain, which appears as if formed of fmall
fcales. It is diflinguiflied into hot fhort
iron, and cold fhort iron. The caufe of
this brittlenefs is at prefent known : the
hot fhort iron contains much more fiderite
than other iron, and the quantity of this
martial phofphoric fait is lefs and lefs in
other iron, to the foftefl, which contains
none at all. In order to feparate this fait
from iron, and to determine its quality, the
metalisdirTolvedinfpiritofvitriol,andawhite
precipitate, confifting of fiderite, fubfides
gradually, which is collected and weighed.
Steel formed by forging, is fcarcely ever
perfect, and is befides in fmall quantity :
but iron may be converted into fteel by ar-
tificial means. For that purpofe fhort bars
of iron are inclofed in an earthen box or
veffel, filled with a cement, commonly com-
P 4 pofed

232 IRON.

pofed of very combuflible matters, fuch as
foot, or animal oil, to which is ufually ad-
ded, allies, calcined bones, marine fait, and
fal-ammoniac. The box being well clofed,
is heated for ten or twelve hours, till the
bars become white, and are ready to melt.
In this operation the iron becomes purified,
and is completely reduced by the affiftance
of the combuflible matters with which it
is furrounded ; the portions, which were not
perfectly in the metallic ftate, affume that
ftate; and the fiderite is intirely decompofed.
Astothefalineandearthy matters which were
added, is not well known, whether they are
of any advantage to the procefs. Steel pre-
pared in this manner is called cemented fteel,
and appears to be iron in the pureft ftate.*

Steel

* At the time of this part of his work going to prefs, the
ingenious author does not feem to have been in pofTeflion
of the third volume of Bergman's opufcula, as he certain-
ly would not in' that cafe have retained the doctrine of Mac-
quer, refpecting the nature of fteel. Steel is found to con-
fift of iron in an intermediate ftate between caft iron and
iron which is foft, tough, and malleable. The iron run
from fome German ores is found to be good fteel, when
forged only to a certain point. Caft iron, as Reaumur
flifcovered, may be brought by cementation with animal afhes,
into a ftate refembling fteel, and by a longer continuation
of the procefs, it refembles forged iron. This manage-
ment, however, is lefs effectual than the ufual method, pro-
bably becaufe the impurities of caft iron are not removed by
it. The chief differences in iron, as Bergman, in his ad-
mirable treatife, de Analyfi Ferri, teaches us, appear to de-
pend or* the prefence or abfence of plumbago. When caft

iron

IRON. 233

Steel may be converted again into iron,
by cementation with calcareous earth and
lime, which appear to be proper fubfHnces
to calcine part of it.

It is evident that all the preparations to
which iron is fubje&ed, are neceffary only,
becaufe that metal being more difficult to
fufe than the others, is never perfeftly puri-
fied by a fingle fufion.

There are fome iron ores, particularly the
black iron ore, as for example, that of the
Ifland of Elba, in which this metal is fo
abundant, and fo little altered, that noth-
ing more is neceffary than to melt it. It
is fufficient if thefe be foftened under the
coal in the refining furnace, and conveyed
from thence to the hammer. This is cal-
led the Catalan method, and can only be
ufed with ores that contain but a imall
quantity of fuch foreign matter »s are capa-
ble of being converted into fcoria?.

Spathofe iron ores afford an iron fo pure
and fo foft, that they are commonly called
ileel ores.

iron is diffolved in the vitriolic acid, the undiiTolved refidue
is found to confift chiefly of this mineral. Steel in the
fame circumftances affords lefs plumbago, and tough malle-
able iron leaves fcarcely any refidue. It follows therefore,
that caft iron confiits of the metal combined with plumbago,
which is a kind of fulphur : lteel is a more perfect iron,
nearly as malleable in its foft irate as forged iron ; but in
its hard ftate, as brittle as crude caft iron. Pure forged
iron is the metal itfclf alone. T.

The

234 IRON.

The chemical properties of iron are very
numerous, and in order that they may be
the more perfectly underflood, we fhall con-
fider them as they exift in the pureft fleel.

Steel expofed to a lefs heat than ignition,
affumes feveral {hades of colour. It becomes
fucceffively white, yellow, orange, red, vio-
let, and laftly blue, which colour remains a
confiderable time •> but if the heat be raifed,
it changes to a difagreeable water colour.
Steel ftrongly heated becomes red and fpark-
ling, afterwards appears of the colour of
ftrawberries ; and laftly, very white and
dazzling; it burns with a fenfible flame.
It does not melt but by an extreme heat.
When thrown in filings in the midft of a
burning fire, or even through the flame of a
taper, it fuddenly^ takes fire, and produces
very brilliant fparkles. Thefe are fimilar
to thofe produced by the ftroke of the fteel
againft flint, and if collected on a white
paper, they are found to be metallic, and
refemble a kind of fcoriae. Common iron
expofed to the focus of the lens of M. De
Trudaine, fuddenly throws out inflamed
and burning fparkles. Macquer, who melt-,
ed fteel and iron in this lens, obferved, that
fteel was the moft fufible, which no doubt
arifes from the purity and homogeneity of
this metal. Iron melted and fuflfered to
cool flowly, takes a peculiar cryftalline
form, as we have already obferved. M.

Monger

IRON. 235

Mongez defcribed it to be a pyramid, or
three or four fides.

The blow pipe, with vital air, caufes the
filings of iron to burn as rapidly as the
focus of the lens of the Garden de 1'Infant.
If an iron wire turned in a fpiral form, and
terminated by a fmall piece of lighted quick
match, be plunged into a veffel of vital air,
the metal fuddenly catches fire, and burns
with a very remarkable degree of rapidity
and deflagration. Steel, though very hard
and refractory, is very eafily calcined ; when
it begins to grow red, it combines with the
bafe of air, and burns without any apparent
flame at that heat. A bar of iron kept red
hot for a long time, becomes covered with
fcales, which may be beat off with the ham-
mer. In thefe however, the metal is only
partly calcined, fince they are attractable by
the magnet. A more perfect calx of iron is
made, byexpofingfilings of fteel to heat under
a muffel, when they become converted into a
powder of a reddifti brown, not attractable
by the magnet, which is called aftringent
faflron of Mars. This martial calx differs
according to the ftate of the iron, and the
degree of calcination it has been fubjected to.
Some aftringent faffrons of Mars are of a
yellow brown, others the colour of a cho-
colate brown, and others of a beautiful red,
fimilar to carmine. The aftringent faffron
pf Mars, expofed to a very ftrong heat,

melts

2%6 IRON.

melts into a blackifh porous glafs, which
is partly reduced by flowly heating in clofe
veffels. If it has been a fhort time expofed
to the air, it gives out a certain quantity
of cretaceous acid during its reduction,
which fhews that it attracts this acid from
the atmofphere. All the calces of iron
have this character in a greater or lefs de-
gree; we have already pointed it out in the
cafe of lead, in which the property is much
more eminent.

The aftringent faffron of Mars is eafily
reduced with combuftihle matters. When
mixed with a fmall quantity of oil, and
flowly heated in a crucible, it becomes
black, and is ftrongly attracted by the mag-
net. This procefs affords, a very gpod kind
pf martial ^Ethiops.

The pureft iron expofed to moift air,
foon lofes its metallic brilliancy, becomes
covered with a pulverulent yellowifti cruft,
of a lighter colour than the aftringent faf-
fron of Mars. This matter is ufually called
ruft. Common iron is rnuch more fubject
to ruft than fteel -, the more this metal is
divided, the more rapid is its alteration by
expofure to air. In this manner the pre-
paration, known in pharmacy under the
name of aperitive faffron of Mars, is pre-
pared. Steel filings are expofed to the air,
and moiftened with water, by which means
they very quickly ruft. The fame procefs

with

IRON. 237

with iron in the ftate of iEthiops, is ftill
more expeditious. In this alteration the
metal is agglutinated, and forms mafles
which muft be levigated before they can be
employed in medicine. It was formerly
thought that the Tuft of iron was produced
by the air, but it is at prefent known, that
this metal is calcined by water. My own
experiments lead me to think, that the
aperitive faffron of Mars is a combination
of the calx of iron with the cretaceous
acid. I have diftilled the faffron of Mars
in the pneumato-chemical apparatus, and
obtained a large quantity of cretaceous acid.
The iron was changed into a black powder,
ftrongly attracted by the magnet. M. Joffe,
apothecary at Paris, has communicated to
the Royal Society of medicine, a like pro-
cefs for quickly obtaining the martial
i*Ethiops. He recommends igniting the ape-
ritive faffron of Mars in a retort, to which
a receiver, pierced with a fmall hole, is
adapted without luting; by this means the
heat difengages the cretaceous acid which
Mr. Joffe fuffers to efcape by the opening
in the retort, and the iron remains pure.
I have often caufed the pure vegetable alka-
li to cryftallize by this means ; the infide of
the receiver being previoufly melted with a
folution of that fait : for the cretaceous acid
of the iron, together with the cauftic ve-
getable alkali, forms that kind of neutral

fair,

238 IRON*

fait, which I have called chalk of pot-am.
I have made many other experiments on the
ruft of iron, which are explained in one of
my memoirs. (Memoires et Obfervations
deChimie, 1784.) and various experiments
have convinced me that this matter is a true
neutral fait, formed of the calx of iron and
cretaceous acid •> for which reafon I have
given it the name of martial chalk, to dif-
tinguifh it from the true calx of the metal.
This fait is abfolutely the fame with that
which Bergman calls aerated iron. This
theory poffefles the advantage of having been
adopted by Macquer, and perfectly explains
the caufe why iron rufts very quickly in a
humid and impure airj why it becomes
rufted fo quickly, and to fuch a depth, in
places where the air is vitiated by the refpi-
ration of animals, by combuftion, by animal
vapours, and in ftables, neceflary houfes, &c.
Iron is the moft alterable, by contadt of air,
of all metallic fubftances ; and this altera-
tion is not confined to its furface; bars of
iron of confiderable thicknefs, are often
found to be rufted quite to the middle.

Cold water has a confiderable aftion on
iron, dividing it, and even diflblving a part,
according to the experiments of Mr. Mon-
net ; the purer the iron, and the more air
the water contains, the larger is the quan-
tity taken up. When iron filings have been
agitated for fome time in water, the metal

appears

IRONT. 239

appears to be extremely divided, aud the
turbid water, after decantation, depofits a
very black and fubtle powder, called the
martial /Ethiops of Lemery. This powder
muft be carefully dried in a clofe veflel, by
a mild heat, left the contact of the air Lhould
ruft it. The martial iEthiops is ftrongly
attracted by the magnet, and is in the firft
ftage of calcination by water. As this ope-
ration is very long and delicate, many che-
mifts have endeavoured to render it more
eafy in the practice. Rouelle employed the
mouffoirsdelaGaraye for this preparation, and
obtained a very fine Ethiops in much lefs
time than the procefs of Lemery requires to
afford it. I think that the procefs of Mr.
Jofie, which is much more expeditious,
may be advantageoufly fubftituted; and feve-
ral other proceffes for preparing Ethiops
mineral are related in the following pages.

Bars of fteel heated, and fuddenly plunged
in cold water, acquire a very coniiderable
degree of hardnefs, and become brittle;
thefe qualities are fo much the more emi-
nent, in proportion as the fteel was hotter,
and the fluid in which it is plunged, colder.
This operation is called tempering. The
degrees of hardnefs of fteel may be varied
at pleafure ; and it may likewife be eafily
deprived of its hardnefs, by heating it to
the fame degree it had before the temper-
ing, and fuffering it to cool gradually. This

effect

24O IRON,

effect of the water appears to coniift in a
change in the difpofition of the parts of the
fteelr produced by the fudden cooling, which
impedes its cryflallization. All metals are
capable of acquiring hardnefs by the fame
procefs. But this quality is the more fen-
fible, accordingly as the metal is lefs fufible;
a property which iron poilefles in a very low
degree.

It has been difcovered about two years,
that a ftrong action is exerted between water
and iron. M. Lavoifier having expofed
iron with water in a glafs veflel, over mer-
cury, obferved, that the iron became rufty,
and the water was diminifhed in proportion
as the elaftic fluid was difengaged, which
filled the fuperior part of the apparatus.
This fluid was inflammable gas ; the iron
had increafed in weight, and was calcined.
M. Lavoifier fufpecfted that water contains
pure air, and that this fubftance being united
to the iron, the inflammable gas, or other
principles of the water, was difengaged in
the fame proportion. He afterwards made
the experiment, in conjunction with M.
Meufnier, in a more decided manner, by in-
troducing the vapour of water into a red
hot gun barrel y he obtained a large quan-
tity of inflammable gas ; the inner part of
the gun barrel became increafed in bulk,
and affumed a black, brittle, lamellatcd ap-
pearance, fimilar to the iron ore of the ifland

of

IRON. 241

of Elba. The metal was increafed in weight,
and the addition, together with the weight
of inflammable gas, correfponded perfectly
with that of the quantity of water deftroy-
ed. The portion of iron calcined in this
experiment, was found feparate from that
which had not fuftained the fame altera-
tion ; it formed an interior cylinder, thick-
er, and of a texture colour, confidence, and
form, very different from that of the exter-
nal part. The heat of red hot iron is necef*
fary, in order to fucceed this experiment,
becaufe it Angularly favours the feparation
of the principles of the water by the metal,
for which reafon, when the gun barrel is
not well ignited, and the water does not
pafs in a ftrongly elaftic ftate, inflammable
gas is not difengaged, the water not being
decompofed ; a want of attention to this
circumftance, has caufed feveral philofo-
phers, who did not fufliciently heat the iron,
and introduced liquid water, to deny the
decompofition of that fluid, though its ana-
lyfis, accurately made by this experiment,
is confirmed by the fynthefis, as Meffrs.
Mongez and Lavoifier have demonftrated.
There are many other circumftances, in
which water is thus feparated into its prin-
ciples, and contribute to the production of
many very important phenomena, as will
be hereafter explained.
Vol. III. 4 Q_ Iron,

242 IRON.

Iron, in its metallic ftate, does not unite
to earthy and ftony matters ; but the calx of
iron facilitates the vitrification of all forts
of ftones, and colours them either green or
brown. The colour communicated by the
calces of iron, are exceedingly various, ac-
cording to the peculiar ftate of the calces,
which approach more or lefs to the me-
tallic ftate. Thefe calces have likewife
the property of affording various degrees of
confidence to earths, with which nature or
art has mixed them, by the afliftance of
water.

Barytes, magnefia, and lime, have no evi-
dent adtion on iron.

The pure fixed alkalies, and the volatile al-
kali, when diftblved in water, a& fenfibly on
this metal : after feveral days digeftion the
fluids become turbid, and afford a fmall
quantity of iEthiops, which falls down; a
certain quantity of inflammable gas being
at the fame time difengaged, as the che-
mifts of Dijon have obferved. This cir-
cumftance proves, that water contributes
greatly to the effed.

Iron is foluble in all the acids. M. Mon-
net has obferved, that oil of vitriol does not
adt on this metal, unlefs it be boiling.
When this acid is diftilled to drynefs from
iron, the retort is found to contain flowers
of fulphur fublimed, and a white vitriolic
mafs, partly foluble in water, which, how-
ever,

IRON; 243

ever, does not afford cryflals, becaufe it has
been decompofed by heat. If the vitriolic
acid, diluted with two parts of water, be
poured on iron filings, it diffolves the metal
very readily, without the affiftance of exter-
nal heat. The folution is attended with
the difengagement of a large quantity of
inflammable gas, which may be made to
detonate with a confiderable noife, by ap-
plying a lighted candle to the aperture of
the veffel, after having clofed it for a fhort
time with the hand. The inflammable gas
burns with a reddifh flame, and very often
exhibits fmall fparkles, limilar to thofe of
iron filings. Macquer fuppofed, that the
vitriolic acid in this combination difen-
gaged a large quantity of phlogiflon from
the iron, and that the inflammable gas was
derived intirely from the metal. This opi-
nion appears to be founded on a circum-
ftance formerly believed, viz. that inflam-
mable gas might be extracted from iron
alone, without addition, by the Ample ac-
tion of heat ; but it is now proved, that
iron does not afford inflammable gas by heat,
but in proportion to the water or the moif-
ture which may be prefent; and it is equally
proved, that the water added to the vitriolic
acid in the prefent experiment, is the only
fubftance which produces the inflammable
gas by its decompofition. 1. Becaufe the vi-
triolic acid, in a concentrated ftate, affords
Q^ 2 only

244 IRON.

only fulphureous gas. 2. In the concen-
trated ftate, it does not attack iron, with-
out difficulty, and by the affiftance of a
ftrong heat. 3. As foon as water is added,
the adtion becomes much more rapid, and
the production of inflammable gas takes
place. 4. The quantity of concentrated
vitriolic acid employed, is partly decom-
pofed by the iron when water is not added ;
whereas, the acid intirely combines with
the calx of iron, without fuffering any de-
compofition when water is added to the fo-
lution. It is therefore the water which
calcines the iron in this operation, as M.
De la Place long fince fufpedted, and Meffrs.
Lavoifier and Meufnier have proved.

In proportion as the diluted vitriolic acid
adts on the iron, a portion of the metal is
precipitated in a black powder, which Stahl
fuppofed to be fulphur, but M. Monnet
found, on examination, to be martial iEthi-
ops. The portion of black calx of iron
produced by the water, appears to be fuper-
abundant to the faturation of the acid.
When one part of the iron is combined with
one part of the acid, though the latter be
far from faturation, the folution ceafes, and
the metal is no longer a£ted on. M. Mon-
net, who made this obfervation, remarks,
that when water is poured on the mixture,
the action of the acid commences again ; a
phenomenon which arifes from the water of

the

IRON. 245

the fpirit of vitriol being abforbed by the
martial vitriol already formed ; and the
portion of the acid, which is not yet fatu-
rated, having no power to acfl on the iron,
till a new quantity of water begins the cal-
cination of that metal. The vitriolic acid
diffolves more than half its weight of iron,
and the folution filtered and evaporated, af-
fords, by cooling, a tranfparent fait, of a
beautiful green colour, cryftallized in rhom-
boids, called martial vitriol, or green cop-
peras.

Martial vitriol is not made in the direct
way, becaufe it is abundantly afforded by
nature, and is eafily extracted by art from
martial pyrites. The pyrites being expofed
to air for a certain time, become decompos-
ed by moifture ; a white effiorefcence ap-
pearing on their furface, which, by folution
in water and cryflallization, is found to be
vitriol. This decomposition of pyrites, ac-
cording to Stahl, depends on double affini-
ties. Sulphur, a compound of phlogifton,
and the vitriolic acid, is not decompofable
by water, nor by iron alone; but when thefe
fubftances are united, the iron feizes the
phlogifton of the fulphur, its acid uniting
to the water, and diflblving the metal.
The pyrites, which are the lean: fufceptible
of effiorefcence -, as for example, thofe which
are the moil: brilliant, being roafled to drive
ofFa portion of the fulphur they contain, and
Q^3 after-

246 IRON,

afterwards expofed to the air, readily efflo-
refce. The vitriol is feparated by wafhing,
and the folution of this fait immediately de-
pofits a certain quantity of iron, in the ftate
of ochre, for which reafon the fluid is not
evaporated, for the purpofe of obtaining
cryftals, till this precipitate has fallen.
Modern chemifts think, that in the vitrioli-
zation of the pyrites, the fulphur which is
in a ftate of extreme divifion, combines
with a portion of pure air, and forms oil
of vitriol, which, being diluted by the
vapours which float in the atmofphere,
unites with heat to the iron, and dif-
folves it. The neceflity of the contact of
air for the efflorefcence of pyrites, gives
much force to this opinion -> and the moif-
ture, which greatly favours the vitrioliza-
tion, adls in this cafe as it does in the dired:
folution of iron ; this is the caufe of the
inflammable gas which is difengaged when
the operation is made in a vacuum.

Martial vitriol is of an emerald green,
and has a very ftrong aftringent tafte ; it
fometimes reddens fyrup of violets, but this
cffedt is not conflant ; its cryftals contain,
according to Kunckel and Monnet, more
than half their weight of water 5 if it be
heated brifkly, it liquifies like all falts,
which are more foluble in hot than in cold
water ; it becomes of a whitifh grey by
drying; if it be heated by a more violent,

iirea

IRON. 247

fire, a portion of its acid efcapes under the
form of fulphureous gas, and the fait affumes
a red colour, in which fbte it is named
colcothar. Martial vitriol calcined to red-
nefs, attracts the humidity of the air very
fenfibly, on account of a portion of vitrio-
lic acid it contains. Martial vitriol diftill-
ed in a retort placed in a reverberatory
furnace, affords firft, water flightly acid ;
and when the heat is very itrong, the oil of
vitriol paffes over of a black colour, and
exhaling a fuffocating fmell of fulphureous
vitriolic acid. Thefe characters depend on
its being deprived of a part of its oxygi-
nous principle which is fixed in the iron,
according to the doftrine of the gafes ; to-
wards the end of the operation, the acid
which comes over, takes a concrete and cry-
ftalline form, and is diftinguifhed by the
name of glacial oil of vitriol. This experi-
ment, defcribed by Hellot, did not fucceed
with Baume, though it is admitted as cer-
tain by moft chemifts. When glacial oil
of vitriol is diftilled in a fmall retort, it
gives out fuiphureous gas, and comes over
white and fluid; its concrete ftate is there-
fore owing to the prefence of this gas ; it
unites with water with noife and heat, ful-
phureous gas being at the fame time dif-
engaged. The fuming oil of vitriol of
Noorthauffen is of this kind, and the
concrete fait obtained from it by a gen-
tle heat, of which I have given £n ana-

CL4 lyfis

248 IRON,

lyfis in a memoir, to be published among
thofe of the Academy.

Therefidue of martial vitriol, after diftil-
lation, is red, and fimilar to colcothar,
Whenwafhed with water, a white fait little
known, and named fait of colcothar or
fixed fait of vitriol, is feparated ; a red infipid
earth, which is a pure calx of iron, and is
called fweet earth of vitriol, remains be-
hind.

Martial vitriol expofed to the air be^
comes yellowifh, and covered with ruftj
the vital air being gradually abforbed, cal-
cines the iron more and more, fo that it
cannot remain united with the vitriolic
acid. The folution of martial vitriol exhi-
bits the fame phenomenon, by the contact
of the atmofphere, and both may ferve the
purpofe of an eudiometer. This fait is fo->
luble in twice its weight in cold, or in a
lefs quantity of hot water; but as foon as
the water is faturated, it appears turbid, by
a quantity of ochre which feparates ; the
fluid being filtered, and fuffered to cool,
affords rhomboidal cryftals, of a pale tran-
fparent green ; the remaining fluid being
again evaporated, affords a new quantity of
cryflals by cooling ; and when all the cry-
ftals have- been obtained, that the folution is
capable of affording, a mother water, of a
blackifh green, or brown yellow, remains,
which is no longer capable of cryftallizing;

this

IRON. 249

this being evaporated by a ftrong heat, and
fuffered to cool, appears to be a foft un&uous
mafs, ftrongly attracting the humidity of
the air ; when evaporated to drynefs, it af-
fords a greenifh yellow powder. According
to Monnet, the mother water of vitriol con-
tains iron in the flate of a perfecft calx: this
chemift afcertained the fad, by immediately
diflblving, with the affiftance of heat, a true
calx of iron in the vitriolic acid j the folu-
tien was brown, and incapable of cryftalli-
zing,

The calx of iron may be feparated from
the mother water of vitriol, not only by the
earth of alum, but likewife by copper and
iron filings, which does not happen to per-
fect martial vitriol. A well charged folu-
tion of martial vitriol being expoied to the
air, is converted, after a certain time, into
vitriol mother water, fimilar to the forego-
ing, by attracting the oxyginous principle of
the atmofphere.

Martial vitriol is decompofable by lime
and alkalies : lime-water poured into a folu-
tion of this fait, forms a precipitate in flocks,
of a deep olive green; a portion of this preci-
pitate is rediffolved in the lime-water,' and
communicates to it a reddifh colour. I have
communicated two Memoirs to the Aca-
demy, in the years 1777, and 1778, concern-
ing the martial precipitate obtained by
gauflicand non-cauilic alkalies, in which I

have

have carefully defcribed the phenomena of
their precipitations, and the ftate of the iron
in the different circumftances. I fhall here
relate the principal circumftances relative to
vitriol. Cauftic fixed alkali precipitates the
vitriolic martial folution in flocks, of a deep
green, which are diflblved again by the al-
kali, and form a kind of martial tincture, of
a beautiful red ; when lefs of the alkali is
added, the precipitate may be collected, and
a blackifli iEthiops is obtained ; if it be
dried quickly in clofed veflels, without thefe
two precautions, the iron quickly becomes
ruft^d, becaufe it is very much divided and
moilt The vegetable alkali fatur?* h

the cretacetous acid, or chalk of pot-afh.
forms a precipitate of a gre< lift] white co-
lour, not diflbluble in the alkali ; thi dif-
ference arifes from the prefence of the cre-
taceous acid, which feizes the iron, in pro-
portion as itfelf is feparited from the alkali
by the vitriolic acid ; the pure or cauftic
volatile alkali, feparates from the folution
of martial vitriol a precipitate of fo deep
a green, that it appears black; it is not
foluble in the volatile alkali. By fudden
drying, without the contact of the air, it
may be obtained black, and obedient to the
magnet. The precipitate formed by con-
crete volatile alkali, or ammoniacal chalk, is
of a greenifh grey : it is partly re-diflblved in
the fait, and communicates a red colour; an
event direftly contrary to what happens

when

IRON, 251

when the precipitations are made by fixed
alkali.

Vegetable aftringent matters, fuch as nut-
galls, fumac, hulks of nuts, quinquina, cy-
prefs nuts, logwood, tea, &c. have the
property of precipitating martial vitriol in
a black fecula : this precipitate, which
cannot be miftaken for iron, is fo ex-
tremely divided, that it remains fufpended
in the fluid; the addition of gum arabic to
the mixture, caufes the iron to be perma-
nently fufpended, and forms a black fluid,
known by the name of ink. It is not well
decided what happens during this experi-
ment. Macquer, Monnet, and moil che-
mifts, confider the precipitate of ink, as iron
united to a principle of the nut-gall, which
difengages it from the acid ; they feem to
think that this principle is in an oily itate.
M. Gioanetti, phyfician at Turin, has made
many experiments on iron precipitated
from its folutions by aftringents. Thefe in-
quiries, which are to be found in his Analy-
fis of the waters of St. Vincent, fhew, that
the precipitate is not attracted by the load-
ftone; that it becomes attractable by heating
in a well clofed veflel ; that it is foluble in
acids, without eflfervefcence ; that thefe fo-
lutions do not become black on the addi-
tion of frefh galls, which fhews that the
iron is united to the aftringent principle,
and is in the ftate of a kind of neutral fait.
In the third volume of the Elements of

Chemiftrv,

252 IRON.

Chemiftry of the Academy of Dijon, there
is a feries of experiments on the vegetable
aftringent principle, which feem to affimi-
late this fubftance to acids •> in fadt it red-
dens blue vegetable colours, unites to alka-
lies, decompofes livers of fulphur, diffblves
and appears to neutralize metals, decompo-
fes all metallic folutions with particular
phenomena ; rifes in diftillation without be-
ing deprived of its action on metals, and
prefents a great number of other properties,
concerning which, the order we have adopt-
ed will not permit us to enlarge.*

The decompofition of martial vitriol, by
an alkali calcined with bullock's blood, is
a phenomenon ftill more difficult to be
underftood than the adlion of the nut-gall
on this fait; the precipitate obtained is of a
beautiful blue colour, and infoluble in acids.
This precipitate is called Pruffian or Berlin
blue, from the place of its difcovery.

* The valuable refearches of the Academicians of Dijon
on the aftringent principle well deferve to be perufed and
ftudied ; they confiderably add to the labours of MefTrs,
Macquer, Monnet, and Gioanetti, on this important fub-
jecl: ; the fubjecl: is however far from being exhaufted, and
requires to be examined at large, efpecially with the
intention of difcovering the nature of this fingular princU
pie, which is formed in all vegetable aftringent matters,
and appears to be foluble in a great number of menftrua,
fuch as water, acids, alkalies, oils, fpirit of wine, aether, &c.
See the Elemens de Chimie, theorique & pratique, etc.
pour Servir aux cours publics de PAcademie de Dijon,
tome 3. page 403 to 421. Note of the author.

Stahl

IRON. 253

Stahl reports that a chemift, named Dief-
bach, having borrowed fome fixed alkali
from Dippel to precipitate a folution of
cochineal, mixed with a fmall quantity of
alum and martial vitriol, the latter gave
him an alkali from which he had diftilled
his animal oil ; the fait precipitated the
folution of Diefbach of a blue colour. Dip-
pel examined the caufe of this precipitate,
and by a lefs complicated procefs, prepared
the Pruffian blue, which was mentioned in
the year 1710, in the publication of the
Academy of Berlin, but without any detail
refpecting the operations. Several chemifls
laboured earneftly to produce the fame, and
fucceeded. But it was not till the year 1724,
that Woodward publifhed, in the Philofo-
phical Tranfadlions, a procefs for preparing
this colouring fubftance.

To form Pruffian blue, four ounces of
nitre fixed by tartar are mixed with an
equal weight of dried ox's blood; this
mixture is calcined in a crucible till it
refembles coal, and no longer produces
any flame; a fufficient quantity of water is
then added to diifolve all the faline matter,
which is called phlogifticated alkali, and
is concentrated by evaporation ; two ounces
of martial vitriol, and four ounces of
alum, are afterwards difTolved in a pint of
water; the folution of thefe falts is mixed
with the alkaline lixivium, a blueifh pre-
cipitate

254 IfcON.

cipitate falls down, which is feparated by
the filter, and marine acid being poured on
it, it immediately becomes of a more beau-
tiful and deeper blue, and is to be then dried
by a mild heat, or by expofure to the air.

Many chemifts have, fince the time of
Woodward, attended to the theory and
preparation of Pruffian blue. With regard
to its preparation, it is now known that
a great number of fubftances are capable
of communicating to the alkali the pro-
perty of precipitating iron of a blue colour.

Geoffroy, in the Memoirs of the Acade-
my for the year 1725, communicated this
property to alkalis with all kinds of ani-
mal coals. M. Baume affirms, that the
phlogifticated alkali may likewife be pre-
pared by the coals of vegetable fubftances,
provided a ftronger heat be ufed. Spiel-
man made it with bitumens, and Brandt
with foot. The manufactories of Pruffian
blue are become numerous, and each, as it
feems, ufe different matters for their pre-
paration. M. Baunach informs us, that in
Germany, the nails, horn, and fkins of
oxen are ufed. All animal matters do not,
however, appear proper to phlogifticate the
alkali ; they have in vain attempted to pre-
pare it with the gall of the ox, by a procefs
fimilar to that which is executed with the
blood. I obtained only an alkali, with pre-
cipitated vitriol of a greenifh white, and the

preci-

IRON. 255

precipitate was entirely foluble in marine
acid.

Chemifts have differed greatly on the
theory of Pruffian blue. Brown and Geoff-
roy confidered it as the phlogiftic part of
iron, developed by the lixivium of blood,
and transferred to the earth of alum : the
Abbe Menon imagined that it was the
pureft iron, difengaged from every foreign
fubftance by the phlogifticated alkali : Mac-
quer, in a Memoir which has juftly de-
fended the name of mafter-piece from every
chemift, and is inferted in the Memoirs of
the Academy for the year 1752, has re-
futed the opinions of thefe authors ; he
thinks the Pruffian blue confifts of iron,
combined with an excefs of the inflamma-
ble principle afforded by the phlogifticated
alkali, which this laft obtained from the
blood. He obferves, 1. That Pruffian
blue, expofed to the fire, lofes its colour,
and becomes fimple iron. 2. That this blue
is not at all foluble in acids, however ftrong.
3. That alkalies are capable of diffolving
the colouring matter of Pruffian blue, and
of becoming faturated therewith : for this
purpofe, an alkaline lixivium is to be heat-
ed on Pruffian blue, till it ceafes to dif-
colour that pigment. This alkali, faturated
with the colouring matter of Pruffian blue,
is found to be deprived of moft of its
properties -, it is no longer cauftic nor ef-

fervefcent

256 IRON.

fervefcent with acids ; among the earthy
falts it decompofes only the barytic; it pre-
cipitates all metallic falts, and it feems that
this decompofition takes place by virtue of
a double affinity, that of the acid on the
alkali, and that of the metallic calx on the
colouring matter united to the fait. An
alkali in this manner, is capable of dif-
colouring the twentieth of its weight of
Pruffian blue, and is then faturated with
the colouring matter; acids difengage a
fmall quantity of blue fecula from it, and
it immediately precipitates martial vitriol
in the form of perfect Pruffian blue.

With regard to the alkali prepared in the
ufual way, Macquer obferves, that it is
very far from being intirely faturated with
colouring matter; and that, on this account,
it firft precipitates the folution of martial
vitriol of a green colour : in fact, it is the
portion of alkali which is faturated that pre-
cipitates the iron of a blue colour; but the
portion which is not faturated precipitates
the iron in the ftate of ochre, which renders
the blue precipitate green by the mixture of
this laft colour with yellow. In this inge-
nious theory, the acid poured on the precipi-
tate ferves to diffolve the portion which is not
in the ftate of Pruffian blue, and confe-
quently renders the colour of this laft more
intenfe; the alum added to the folution of
vitriol faturates the alkali, which is not

ch arged

IRON. 257

charged with colouring matter, and the
earth of this fait, depoiited with the Pruf-
fian blue, renders it lefs deep. As it is necef-
fary to pour an acid on the precipitate of
martial vitriol, in order to render the Pruf-
fian blue more lively; this acid may be added
to the alkali, before it is ufed to precipitate
the iron, in which cafe the acid faturating
the portion of pure alkali, does not unite to
that which is charged with the colouring
matter, and therefore leaves it capable of in-
ftantly forming a fine Pruffian blue. This al-
kali partly phlogifticated by bullock's blood*
may be fully faturated, by digefting it on
Pruffian blue, till it ceafes to deprive it of its
colour. Macquer obferved, that this alkali
faturated with acid, is a good teft to the pre-
fence of iron in mineral waters ; but M.
Baume has remarked, that the liquor itfelf
contains a certain quantity of Pruffian blue,
which might be produdtivb of error : he
therefore propofes to digeft it for a fufficient
time in a mild heat, with a fmall quantity
of vinegar, that it may depofit all the blue
matter it contains.

Such was the admirable feries of experi-
ments made by Macquer on the Pruffian
blue ; but this celebrated chemift was
himfelf fenfible how much remained to be
done, efpecially with refpedl to the nature
of the colouring fubftance : he could not
be perfuaded that it was pure phlogifton,
Vol. III. R becaufe

258 IRON.

becaufe on that fuppofition it was difficult
to determine how the iron, overcharged with
that principle, became deprived of the pro-
perty of obeying the magnet, and of fallibi-
lity in acids, which, according to Stahl, are
confequences of the prefence of phlogifton
in this metal. M. De Morveau is the firft,
who, in his excellent DifTertation on phlo-
gifton, has attempted to difcover the nature
of the colouring part of Pruffian blue. From
two drachms of this compound he obtain-
ed by diftillation twenty-two grains of a
yellow empyreumatic liquor, which caufed
an effervefcence with aerated alkali, ftrongly
reddened blue paper, and of which Geoffroy
and Macquer, who likewife diftilled Pruffian
blue, have made no mention.

Mr. Sage, in the year 1772, communicated to
the Electoral Academy of Mentz, a Memoir
on the phlogifticated alkali, which he calls
animal fait. The lixivium of the fixed alkali
treated with blood, and digefled on the Pruf-
fian blue, according to the manner of Mac-
quer, is, as Mr. Sage affirms, a neutral fait,
formed by the animal acid and fixed al-
kali, and affords, by fpontaneous evapora-
tion, cryftals which are either cubical, oc-
tahedral, or quadrangular prifms, terminat-
ed by four fided pyramids. This fait de-
crepitates on charcoal, melts by a violent
fire into a femi-tranfparent mafs, foluble in
water, and proper to form Pruffian blue.

Mr.

IRON. 259

Mr. Sage thinks, that the acid which neu-
tralizes the alkali in this fait, is the phof-
phoric, becaufe when a mixture of alkali
and bullock's blood are ftrongly heated,
it meits and emits acrid vapours, accompa-
nied with white and brilliant fparks, which,
according to him, are burning phofphorus.
This opinion refpedling the acid of the
Pruffian alkali would be proved, if, on the
one fide, phofphorus were obtained by dif-
tillation with charcoal, which likewife would
take place with refpedl to the Pruffian blue ;
and if, on the other fide, Pruffian blue could
be formed by combining the fufible or phof-
phoric fait with bafe of vegetable alkali,
with a martial folution : but as Mr. Sage has
not related any experiments of this nature in
his Memoir, his theory cannot be admitted.

The chemifts of the Academy of Dijon
have adopted part of this laft dodtrine : in
their Elements they confider the phlogifti-
cated lixivium as a folution of a neutral fait;
they advife the cryftallizing it by evapora-
tion, inftead of purifying it by vinegar, as
Baume propofed. This fait is very pure ac-
cording to them, and caufes a detonation
when thrown on nitre in fufion : they have
faid nothing concerning its decompofitions,
and the nature of its principles ; they call
it the cryftallized Pruffian alkali.

Bucquet having precipitated by the ma-
rine acid, and filtered a lixivium prepared
R 2 for

26o IRON*

for Pruffian blue, obferved, that this alkali
though very clear, and apparently deprived
of all the Pruffian blue it might contain,
neverthelefs depofited a blue powder. After
having filtered it more than twenty times
in the fpace of two years, to feparate the
Pruffian blue which was depofited after each
filtration, he at laft found, that the liquor
was no longer capable of affording Pruffian
blue with the folution of martial vitriol.
I have ftill by me a fmall portion of this
lixivium, which has been prepared for near
eight years : it is two years fince it has de-
pofited any precipitate, but it has depofited
a light blueim covering on the fides of the
glafs in which it is contained, and has itfelf
preferved a fimilar colour. I have had occa-
sion twice to obferve this phenomenon, fince
I firft heard it mentioned by Bucquet, in
his Lectures, and I think it is conftant.
The Duke de Chaulnes fhewed Macquer a
phlogifticated lixivium, which did not af-
ford Pruffian blue when previoufly mixed
with an acid. This chemifl fuppofes that
it arifes from its having been prepared in
metallic veifels. From the obfervation be-
fore recited, Bucquet fuppofed, i. That the
Pruffian blue is entirely contained in the
alkali, which ferves to precipitate it. 2.
That acids alone are fufficient to feparate it
from the alkali. 3. That when this alkali,
at the end of a certain time, has depofited

all

IRON. 26l

all the colouring matter it contains, it is
no longer proper to form Pruflian blue.

The Journal de Phyfique for the year
1778, contains obfervations on Pruffian blue,
by M. Baunach, apothecary at Metz, which
greatly favour the opinion of Bucquet. After
having defcribed the procefs employed in
the manufactories in Germany to prepare
Pruffian blue, M. Baunach affirms, that the
lixivium made in thefe manufactories by
the fufion of alkali, and of the hoofs, horns,
and ikins of oxen, precipitates all the me-
tals, and even calcareous earth, of a blue
colour. This alkali diffolves the metals
after having precipitated them, and they
may be feparated of a very beautiful blue
colour by the marine acid. The fingular
faCts related in this memoir, fuch as the
diftillation of Pruffian blue, produced by
this lixivium, which affords neither oil nor
volatile alkali ; the folubility of the blue pre-
cipitate (formed by the marine acid, poured
on this lixivium) in the nitrous acid ; the
calcareous earth found in folution in the
latter acid, which difcoloured the blue; a
peculiar and phlogifticated earth which he
did not fucceed in diffolving.— Do not thefe
circumftances prove, that this blue is not
of the fame nature wish that which is pre-
cipitated from the common phlogifticat-
ed lixivium, in which Macquer discovered
iron, that could only come from the blood ?
K 3 Since

262 IRON.

Since thefe various inquiries into the na-
ture of Pruffian blue, Mr. Scheele has made a
number of new refearches, which, together
with certain obfervations not yet mention-
ed, tend greatly to elucidate the nature of
this production.

1. The Pruffian blue of commerce, dif-
tilled with a naked fire, affords a very large
quantity of inflammable gas, together with
oil, concrete volatile alkali, and a fmall
quantity of acid phlegm. This gas burns
blue like the inflammable air of marfhes ;
its fmell is empyreumatic ; lime-water gives
it the property of burning with a red colour,
and of detonating with vital air, becaufe it
abforbs the cretaceous acid with which it was
united. M. De Laflbne confidered the gas of
Pruffian blue as a peculiar inflammable gas ;
Pruffian blue, after this analyfis, has the
form of a blackiih powder, obedient to the
magnet. Before it takes this colour, it is
of an orange colour, as M. De Morveau
has obferved : the laft mentioned chemift
even thought, that Pruffian blue, after it
has been converted to an orange colour by
heat, might be ufeful as a pigment.

2. The volatile alkali heated on Pruffian
blue, decompofes it, by feizing its colour-
ing matter, and leaves the iron in the ftate
of ochre. Macquer announced this facft in
the year 1752. Meyer, who fucceeded him,

gave

IRON. 263

gave the name of tinging liquor to this vo-
latile alkali, faturated with the colouring
part of the blue, and advifes the ufe of it in
the analyiis of mineral waters. I have ob-
ferved, that when the cauftic volatile alkali
is diftilled from Pruffian blue, the fluid
which paries over has not the property of
giving a blue colour to martial folutions,
whence it follows, that the colouring prin-
ciple is not as volatile as the alkali. When
a portion only of this fait is diftilled over,
the refidue is of an olive green ; if this be
diluted with diftilled water and filtered, it
is found to be charged with the colouring
matter, and affords a very lively Pruffian
blue, when added to martial vitriol.

3. In the year 1780, I difcovered, that
lime-water digefted by a flight heat on Pruf-
fian blue, diffolves the colouring matter ;
the combination is quickly effected, the
lime-water being coloured, and the Pruffian
blue affuming a rufty appearance ; the lime-
wrater after filtration, is of a beautiful clear
yellow colour, no longer capable of convert-
ing fyrup of violets to a green ; no longer
of an alkaline tafte, nor precipitable by the
cretaceous acid ; it does nut unite with other
acids, and in a word, it is neutralized by
the Pruffian colouring matter, and affords,
when poured on the iblution of martial vi-
triol, a very fine blue, which does not need
an acid to enliven its colour. Mr. Scheele
R 4 fpeaks

264 IRON,

fpeaks of this Pruffian lime-water, doubt-
lefs without being previoufly acquainted
with my experiments on the fubjecl:, though
they were inferted in my Elements of Che-
miftry, printed in the year 1781. He, as
well as myfelf, confiders this combination
as the beft of thofe which have been pro-
pofed as tefts of the prefence of iron, be-
caufe it does not contain Pruffian blue ready
formed,

4. Cauftic fixed alkalies difcolour the
Pruffian blue immediately in the cold. I
have obferved that a confiderable heat is
produced in thefe experiments ; that the
alkalies in a ftate of purity difcolour a much
greater quantity of Pruffian blue than thofe
which are faturated with cretaceous acid,
and that they precipitate a large quantity
of the blue with martial folutions.

5. I found that magnefia has likewife the
property of difcolouring Pruffian blue,
though much more weakly than lime-
water.

6. Pruffian blue thrown in powder on
melted nitre, produces fome fparkles, which
denote that it contains a combuftible mat-
ter.

7. Pruffian blue prepared without alum,
becomes flrongly attracted by the magnet
by a flight calcination ; but the Pruffian
blue of commerce never acquires that pro-
perty by the action of fire,

8, Pruffian

IRON. 265

8. Pruflian blue difcoloured by alkaline
matters, and in the ftate of ochre of iron,
re-afiumes a blue colour when an acid is
added : this circumftance feems to depend
on the whole of the colouring matter not
being taken away by the firft action of the
alkalies, and that a portion is defended by
the external ftratum of ferruginous calx.

All thefe facts fhew, that the colouring
part of Pruflian blue is a peculiar acid,
which faturates alkalis, and forms neutral
falts ; this opinion is adopted by many che-
mifts, and in particular by Mr. Scheele,
whofe refearches on this matter only re-
main to be related. This celebrated chemift
has proved by his experiments, 1. That
a lixivium of blood, or phlogifticated alkali,
is decompofed by the cretaceous acid of the
atmofphere, and that all the other acids
feparate the colouring matter. 2. That
this colouring matter is fixed and retained
in the lixivium, by a fmall quantity of iron,
or of pure vitriol of iron. 3. That when
it is difengaged by acids in diftillation, it
fills the receiver with a vapour, which pre-
cipitates the folutions of iron of a blue
colour. 4. That Pruflian blue diftilled
without addition, as well as the lixivium of
blood, affords, together with the colouring
matter, foreign products, which alter it,
fuch as fulphur; and that the colouring
matter cannot be had pure by this procefs.

5. That

266 IRON.

5. That Pruffian alkalies diililled with the
vitriolic acid, precipitate a large quantity of
Pruffian blue, and afford a liquor charged
with the colouring matter. The portion of
blue precipitated in this operation depends
on the iron diffolved in thefe triple falts, or
combinations of alkalies, colouring matter,
and iron. 6. That the calx of mercury or
red precipitate, feizes the colouring matter
of Pruffian blue, by ebullition, in double
their weight of water ; and that if this
mercurial Pruffian lixivium be diftilled with
the addition of iron and vitriolic acid, the
iron reduces the mercury, and the acid dif-
engages the colouring matter ; this laft be*
coming diffolved in the water of the recei-
ver, in proportion as it is difengaged, and re-
taining a portion of vitriolic acid. To fepa-
rate them, Mr. Scheele mixes a fmall quan-*
tity of chalk with the liquor, and diftills by a
gentle heat : the colouring matter paries
over in a ftate of great purity, and as it is
difengaged in the form of an elaftic fluid,
as M. Mongez alfo obferved, it may be
received in water by the affiftance of tubes,
or the pneumato-chemical apparatus, which
has already been often mentioned.

After thefe refearches concerning the af-
finities of the colouring Pruffian matter, its
adherence with alkalies, and the method of
obtaining it perfe&ly pure, Mr. Scheele, in
a fecond Memoir, inquires into the nature

of

IRON. 267

of this fubftance, and its combinations with
alkalies and metallic calces ; and though
his experiments are numerous, and very ac-
curate, he does not prove that the colouring
matter is a peculiar acid; on the contrary
he proves, that it contains inflammable gas,
volatile alkali, and a carbonaceous principle.
He however has obferved, that it pofleffes
the property of coagulating foap, and pre-
cipitating hepars; and he calls it the colour-
ing acid, in a letter to Mr. Crell. M. De
Morveau calls this fubftance by the name
of Pruffian acid, and diftinguifhes its faline
combinations, according to his nomencla-
ture, by the names of Pruffites ; as for ex-
ample, Pruffites of pot-afh, of foda, &c. In
a note by the tranflator of Mr. Scheele, it is
afferted, that this acid is decompofed by
the acid of nitre, and a procefs of Mr. Weft-
rumb, to obtain the Pruffian alkali in a ftate
of great purity, is given. It conlifts in fatu-
rating cauftic vegetable alkali with the co-
louring matter, digefting it on white lead,
to deprive it of the hepatic gas it may con-
tain, mixing it with diftilled vinegar, and
expofing it to the fan, as Meflrs. Scopoli
and Father Bercia advifed to precipitate the
iron ; after which two parts of rectified fpirit
of wine are added. The Pruffian alkali is then
depofited in lamellated and brilliant flocks,
which being wafhed in frefh fpirit of wine,
is afterwards dried, and diflblved in diftilled

water.

268 IRON.

water. Mr. Scheele, three months after Mr.
Weftrumb, forwarded to Mr. Crell an analo-
gous procefs for obtaining in proof liquor,
which might be depended on as a teft of
the prefence of iron.

Martial vitriol decompofes nitre very rea-
dily. This decompofition is partly due to the
vitriolic acid, which uniting with the alkali
of nitre, difengages the acid of that fait ;
but it is likewife in a great meafure occa-
fioned by the re-adlion of the iron on the
latter acid. If martial vitriol flightly dried
be taken for this experiment, a confiderable
quantity of nitrous acid, very red and fu-
ming, is obtained ; the refidue, by lixivia-
tion, affords vitriolated tartar and fixed alka-
Jine fait; the mild earth of vitriol, re-
mains on the filter : but if ftrongly calcined
vitriol be made ufe of, together with nitre
which has fuffered fufion, the product ob-
tained is very inconfiderable. This produdt
confifts of two liquors ; the one of a dark,
and almoft black colour, floats on the fur^.
face of the other, which is red and pon-»
derous ; for which reafon M. Baume con-*
fidered this liquor as a kind of oil : there
afterwards palfes into the neck of the retort,
a white faline mafs, which attracts the hu^
midity of the air, and is foluble with heat,
and great rapidity in water, emitting a ftrong
fmell of fpirit of nitre, and very thick red
vapours : this folution faturated with fixed

vegetable

IRON. 269

vegetable alkali, affords vitriolated tartar ;
the white mafs therefore is merely oil of
vitriol rendered concrete by a portion of
nitrous gas.

The heavier liquor in the receiver does
not, on examination, appear to differ from
Glauber's fpirit of nitre; but the lighter li-
quid which floats above it, being mixed
with oil of vitriol, produces a flrong effer-
vefcence, and fometimes a dangerous explo-
fion ; almoft all the nitrous acid is diffipat-
ed, and the oil of vitriol takes a concrete
and cryftalline form. Bucquet, who com-
municated this difcovery to the Academy,
had before obferved, that the concrete oil
of vitriol obtained in this diftillation, emits
red nitrous vapours when diffolved in water;
he fuppofed that this acid owes its folid
form to the prefence of nitrous gas, and in
order to afcertain the truth of this conjec-
ture, he attempted to mix the brown black-
ifh nitrous acid which floats over the red li-
quor with very concentrated oil of vitriol ;
but at the very inftant of the mixture of thefe
two fluids, a commotion was excited, of
fo ftrong a kind, that the fpirit of nitre,
poured on the vitriolic acid, was thrown
with confiderable noife to a great diftance ;
the perfon who made the mixture was
covered with the acid, and a large quantity
of red and inflamed pimples inftantly rofe
on his face, which fuppurated like thofe of

the

$J0 IRON.

the fmall-pox; the oil of vitriol foon be-
came concrete, and abfblutely fimilar to
that which is obtained in the diftillation
we have defcribed. From this facl: it ap-
pears, that the acid may become concrete
as well by imbibing nitrous, as fulphureous
gas.

The refidue of the diftillation of nitre
with martial vitriol calcined to rednefs, is
merely af coria of iron, from which a very
fmall quantity of vitriolated tartar may be
obtained by warning.

The folution of martial vitriol is not al-
tered by inflammable gas, becaufe the bafe
of this elaftic fluid has lefs affinity with the
oxygino^s principle than iron, as we have
feen in the hiftory of the deconipofition of
water. M. Monnet has however obferved,
that hepatic gas communicates to vitriolic
mother water the property of affording cry-
ftals.

Liver of fulphur precipitates martial vi-
triol of a blackifh colour; the precipitate
is a kind of martial pyrites.

The nitrous acid is very rapidly decom-
pofed by iron, which difengages a large
quantity of nitrous gas, efpecially if the acid
made ufe of be concentrated, and the iron in
a ftate of divilion : this metal is quickly
calcined by the oxyginous principle it feizes
from the nitrous acid -, the folution is of a
brown red, and depofits calx of iron at the

end

IRON. 27I

end of a certain time, efpecially if in contad
with the air. On the addition of more iron
the acid diffolves it, as Stahl has obferved,
and the calx of iron before held in folution
is precipitated ; neverthelefs, when a weak
nitrous acid is ufed, and iron in pieces, a
more permanent folution may be obtained, in
which the metal adheres more ftrongly to the
acid. This laft combination is greenifh, and
fometimes of a bright red; both folutions be-
come turbid by evaporation, and depolit mar-
tial ochre of a reddifh brown ; but if the lat-
ter be ftrongly concentrated, inftead of afford-
ing cryftals, it takes the form of a reddifh
jelly, which is only in part foluble in water,
the greateft part precipitating- If the nitre
of iron be kept heated, red vapours, in large
quantities, are difengaged, the magma be-
comes dry, and affords a calx of a brick duft
red colour -, this magma, by diftillation in a
retort, affords a fmall quantity of fuming ni-
trous acid, much nitrous gas, and atmofphe-
ric mephitis. Vital air cannot be obtained,
becaufe the iron retains all the oxyginous
principle of the acid ; the calx which re-
mains after the diftillation of nitre of iron,
is of a lively red, and may afford a good co-
lour for painters, &c. The nitrous folu-
tion of iron, however concentrated, did not
appear to afford a precipitate by the addition
of diftilled water j alkalies decompofe it
with different phenomena, according to their

nature;

272 IRON.

nature ; cauftic vegetable alkali precipitates
it of a light brown colour ; the mixture
pafles very quickly to a blackifh brown,
and much deeper than the colour of the firft
folution. This phenomenon arifes from the
portion of the precipitate diffolved by the
alkali, though the quantity be very fmall ;
cretaceous vegetable alkali feparates a yel-
lowifh calx, which quickly becomes of a
beautiful orange red ; if the mixture be agi-
tated, an effervefcence takes place, the preci-
pitate is re-diflblved in much greater abun-
dance than that produced by the cauftic
alkali. M. Monnet took notice of this
phenomenon, and has with juftice attribut-
ed it to the gas which is difengaged. The
folution of iron by fixed alkali, is called
the martial alkaline tin<5ture of Stahl, and
of a very beautiful red. M. Baume recom-
mends a nitrous folution of iron, which is not
highly charged, to be ufed for the preparation
of this tindure : Stahl, on the contrary,
advifes a very faturated folution. M. Mon-
net has obferved, that a yellow folution af-
fords a very large quantity of precipitate,
which is not refoluble by the alkali, and
does not give the colour expedled in the
martial tin&ure ; while a red folution im-
mediately produces it with the fame alkali.
The martial alkalinetinfture of Stahl lofes
its colour at the end of a certain time, and
depofits the calx of iron it contains ; it may

be

IRON. 273

be decompofed by the addition of an acid ;
the nitrous acid Separates a calx of a brick-
duft colour, which is foluble in acids, and
is called Stahl's aperitive faffron of Mars :
pure or cauftic volatile alkali, precipitates
the nitrous folution of iron of a deep, and
almoft black green ; ammoniacal chalk re-
diflblves the iron which it feparates from the
acid, and aflumes a more lively red colour
than the tinfture of Stahl. This folution of
iron by the cretaceous volatile alkali, may
be ufed to great advantage in cafes wherein
a powerful tonic and folvent medicine is
required, .

The nitrous folution of iron highly fatu-
rated, and red, afforded me but a very frnall
quantity of Pruffian blue, by the addition
of an alkali faturated with the colouring
matter. I obtained only a blackifh preci-
pitate, which was re-diflblved by the marine
acid •, the liquor had then a green colour.

M. Marett, fecretary to the Academy of
Dijon, has communicated to the Royal So-
ciety of Medicine, a procefs for making
martial iEthiops very expeditioufly ; it con-
fifts in precipitating the nitrous folution of
iron by the volatile cauflic alkali, and quick-
ly warning and drying the precipitate. M.
D'Arcett, who was appointed by the laft
mentioned fociety, to examine the procefs of
M. Marett, did not conftantly obtain the
fame refult. In my Memoirs on martial
Vol. III. S precipitate.

274 IRONT*

precipitate, I have determined the cafes in
which the experiment of M. Marett fuc-
ceeds, and thofe in which it fails. To obtain
this /Ethiops it is neceffary, i. That the
folution of iron be recently made in the
cold, with a weak nitrous acid, and iron not
much divided, 2. That the volatile alkali be
recently prepared exceedingly cauftic, and
efpecially that it be deprived, by Handing, of
the fmall portion of calcareous earth, and
blackifh combuftible matter which it ufually
carries up from the fal-ammoniac and lime.
3. That the precipitate be immediately fe-
parated from the liquor, and quickly dried
in clofed veffels. Notwithftanding all thefe
precautions, the precipitate is not always
intenfely black, but inclines towards a
brown, and rifes up in the form of fcales,
whofe inferior furface is blackifli ; which
(hews that it is the contact of air which
llightly rufts the fuperior furface. I have
obtained a more beautiful iEthiops, and
with greater certainty, by precipitating the
marine and the acetous folution of iron
by cauftic fixed and volatile alkalies, and
quickly drying the warned precipitates in
clofe veffels ; but I think, notwithftanding,
that thefe iEthiops, however pure they may
be fuppofed, always retain a fmall part of
their precipitants, and their original fol-
vents, as M. Bayen has obferved concern-
ing the precipitates of mercury 5 and that

they

IRON. 27$

they cannot be employed in medicine with
the fame certainty as thofe heretofore de-
fcribed. M. D'Arcett, in his report to the
Royal Society of Medicine, concerning the
procefs of M. Marett, has communicated a
procefs of M. Crohare, for making ^Ethiops
martial. This apothecary, who is well
known by the many chemical experiments
he has fkilfully made, prepares this medi-
cine by boiling water, acidulated by a fmall
quantity of nitrous acid, on filings of iron;
the metal becomes immediately very minute-
ly divided, and affords much /Ethiops. But
I think that the procefs of M. Joffe is prefer-
able to every one of thefe, on account of its
facility in practice, and the confidence with
which its product may be ufed.

As iron is often ufed for obtaining nitrous
gas, it is of confequence to take notice, in
this place, that the gas is never the fame,
but differs greatly, according to the various
circumftances of the folution ; the nature
of the acid more or lefs charged with
mephitis, or the oxigynous principle; the
Hate of the iron, more or lefs greedy of that
principle; the various temperatures, &c.
In general gas, prepared by this procefs,
always contains a confiderable quantity of
mephitis; becaufe the iron is a body which
abforbs the oxigynous principle very ftrong-
ly, and feizes different quantities according
to its nature and its metallic ftate. The ef-

S 2 feds

276 IRON.

fefts of the gas, difengaged by means of
this metal, are therefore uncertain when
applied to eudiometrical refearches. This
truth, which is applicable to all bodies
that feparate the nitrous gas from the acid
of nitre, {hews how little the trials of
air by eudiometers with nitrous gas are
to be depended on. Experiments of this
nature made with liver of fulphur are much
preferable.

The muriatic acid, diluted with water,
diffolves iron with rapidity, and difengages
a large quantity of inflammable air, pro-
duced by the decompofuion of the water,
as happens when this metal is diflblved in
fpirit of vitriol. It was formerly thought
that the inflammable gas produced by the
adtion of iron on the muriatic acid was dif-
ferent from that which is difengaged by
the vitriolic acid : it was thought that this
elaftic fluid was one of the principles of the
muriatic acid -, but the difcovery of the de-
compofition of water by iron, renders it more
probable that this acid, whofe nature is yet
unknown, is not the caufe of the produc-
tion of inflammable gas, but that it arifes
from the water. The folution of iron by
the muriatic acid is attended with much
heat, which continues with the fame force
till the acid is faturated; a proportion of the
iron is precipitated in a true^Ethiops, as hap-,
pens in all the other folutions after filtra-
tion :

IROX. 277

tion : this folution is of a green colour, in-
clining to yellow, and is much more perma-
nent than the two preceding folutions ; when
preferved in a well flopped phial, it does not
depofit iron. I have kept a folution of this
nature for eight years, which has depofited
only a very fmall quantity of powder, of a
pale yellow : but if, on the contrary, it be
expofed to the air, almoft all the iron it con-
tains is precipitated in a few weeks, and
this precipitate is of a lighter colour in pro-
portion as the accefs of the air is the eafier.
It is now proved that this precipitation,
which takes place equally in all the other
folutions of iron, is produced by the bafe
of vital air abforbed by the metal, which
becomes calcined more and more, as I fuf-
pefted in the year 1777. See my Memoires
de Chimie.

Stahl affirmed, that in the combination of
iron with the muriatic acid, the acid affumed
the characters of that of nitre -, but this fadt
has not been obferved by any other chemift.
It feems that Stahl depended only on the
yellow colour of this folution, and the
fmell it emits; a fmell which, in fa<ft, dif-
fers in fome refpefts from that of fpirit of
fait, and approaches to that of the aerated
muriatic acid.

The folution of iron by the muriatic acid
does not cryftallize regularly by evapora-
tion. M. Monnet has obferved, that if

S 3 it

ZJ% IRON.

it be fuffered to cool when it has acquired
the confiftence of fyrup, it forms a kind of
magma, in which may be feen needle-
form flat cryflals, which are very deliques-
cent. This magma melt$ by a very gentle
heat, and feems to deferve the name of
butter of iron -, a greater heat decompofes
it, though lefs readily than martial nitre,
and it affumes the colour of ruft when it is
dry ; the muriatic acid is difengaged from it,
and may be obtained by diftillation; it carries
up with it a fmall quantity of calx of iron,
according to the obfervation of Brandt.
The Duke D'Ayen, in one of the four ex-
cellent memoirs he communicated to the
academy, refpedling the combinations of
acids with metals, has very minutely ex-
amined what paries in this decompofition
of the muriate of iron. The operation
afforded very Angular products : a mild
heat difengaged a phlegm flightly acid;
the muriatic acid then became concentrated,
and its gas, which is much more volatile
than water, was partly fixed by the iron :
a much ftronger heat raifed a portion of this
acid with a fmall quantity of iron, and cry-
flals were formed in the receiver, which were
not deliquefcent ; very tranfparent cryftals
in the form of blades of razors, which de-
compofed the light in the manner of the beft
prifms, and exhibited very beautiful tinges
of red, yellow, green, and blue, were at the

fame

IRON. 279

fame time fublimed to the upper part of the
retort ; at the bottom there remained a ftyp-
tic and deliquelcent fait, of a brilliant co-
lour, and foliated texture, which perfectly
refembled that kind of talc, in large plates,
which is improperly called Mufcovy glafs.
This laft fait, expofed to a violent heat in a
ftone-ware retort, was decompofed, and af-
forded a fublimation ftill more aftonifhing
than the former produces ; it was an opake
matter truly metallic, which, when examined
by the microfcope, exhibited regular cryftals,
or feclions of hexagonal prifms, which the
Duke D'Ayen compares to the pieces inlaid
in floors : thefe cryftals were as brilliant as
the moft highly polifhed fteel, and were
ftrongly attracted by the loadftone. They
confifted therefore of iron reduced to the
metallic ftate, and fublimed.*

Art appears here to imitate nature, which
fublimes iron by volcanic fires, in the form
of brilliant and well polifhed lamina?, refem-.
bling fteel ; fuch at leaft appears to be the
origin of the fpecular iron ore, and of that
of Volvic, which, according to the valuable

* I have in my pofTeffion a black ere of iron, which ex-
hibits very brilliant fmall laminae, of half a line in breadth,
whofe form nearly approaches to that of the cryftals obtain-
ed by the Duke D'Ayen ; they are fmall very thin fcales, of a
very brilliant iron grey colour, placed flopewife, fo as to in-
terfect each other in every direction, and are difperfed on a
reddifh opake quartz, or a kind of coarfe jafper : this beau-
tiful fpecimen came from Lorrain.

S 4 obferva-

28p IRON.

obfervations of M. De L'Arbre, phyfician
at Riom, is always found in the clefts of
lavas.

From thefe details we may perceive how
rich the fcience of chemiftry is in curious
phenomena, and what a fund of difcovery
is held forth to fuch as perform experiments
with all the accuracy of the Duke D'Ayen.
We muft not forget to obferve, that this
reduction of iron favours the dodtrine of *
gafes, and that we may perhaps obtain fimi-
lar refults from many other metallic folu-
tions treated in the fame way,

The muriatic folution of iron, like all other
martial folutions, is decompofed by lime
and alkalies; but the precipitates are lefs al-
tered, and may be eafily reduced, efpecially
fuch as are produced by the addition of
cauftic alkalies. I have before obferved,
that this combination affords the pureft
,/Ethiops by precipitation •> the liver of ful-
phur, hepatic gas, and aftringents, decom-
pofe it like the two others. Laftly, Pruf-
fian alkalies and Pruflian falts precipitate a
beautiful blue powder.

Water charged with the cretaceous acid,
eafily diflblves iron : to form this combina-
tion, nothing more need be done, than to add
iron filings to the acid fpirit of chalk, and
leave the mixture in digeftion for fome
hours ; this fluid, when filtered, has a pene-
trating and rather ftyptic tafte. Meflrs.
Lane and Rouell have taken notice of this

property

IRON. 28l

property in the cretaceous acid. Bergman,
who calls this combination aerated iron,
affirms, that when expofed to the air, it be-
comes covered with a pellicle of rainbow co-
lours ; that it is decompofed by the pure
alkalies, but that thefe falts, when aerated
or cretaceous, do not produce the fame
efFecft. This folution converts the fyrup of
violets to green, and affords very brilliant
Pruffian blue with the calcareous Pruffites;
it affords a precipitate of martial ochre when
left expofed to the air, or when heated : this
combination may be called martial chalk.
Iron has a ftrong tendency to unite with the
cretaceous acid, and nature very frequently
prefents it in this ftate. The muddy iron ores
and fpathofe iron, appear to be entirely form-
ed by this combination; ferruginous mine-
ral waters often contain iron in the ftate of
martial chalk. This fait feparated from the
water and dried, is fcarcely foluble in that
fluid, but it diffolves in a large proportion in
the cretaceous acid fpirit \ from which it is
precipitated, in proportion as the acid is vola-
tilized. The aftion of the fedative and
fluor acids on iron is not known.

This metal decompofes vitriolic falts very
readily, and in particular the vitriol of pot-
afh, and the vitriol of foda. I have treated
thefe falts with iron in a crucible, and have
found them to be in the hepatic ftate. The
lixivium of this kind of hepar, is of a very

deep

282 IRON,

deep green ; a few drops of acid caufed the
colour to difappear very quickly. The
greateft part of the iron calcined by the
oxyginous principle of the vitriolic acid,
remains without diffolving in the lixivium,
and acids difengage a large quantity of he-
patic gas from this calx.

Iron caufes nitre to detonate. When equal
parts of fteel filings, and very dry nitre, are
thrown into a well ignited crucible, a very
rapid commotion is excited, after a little
time, and a great number of brilliant fparkles
fly out of the crucible. When the detona-
tion is ended, the crucible contains a reddifh
calx of iron, of which a fmall portion is
combined with the alkali ; water diffolves
the alkali, and the martial calx remains on
the filter. This is called Zwelfer's faffron of
Mars, and is of a yellowifh red, fcarcely
foluble in acids ; the alkali feparated by the
lixiviation, is caaftic, according to moft
chemifts, who think that metallic calces adt
like pure lime on this fait, charged with
the cretaceous acid.*

* It muft be obferved, that fince the promulgation of
the theory of Dr. Black, refpe&ing the caufticity of lime
and alkalies, the neceflary experiments have not been made,
to afcertain this parity of action between lime and metal-
lic calces ; nothing can therefore be faid refpecting this,
till fuch experiments have been made. Note of the Author.

\ Iron

IRON. 283

Iron decompofes fal-ammoniac, or ammo-
niacal muriate, very readily: two drachms of
fteel filings triturated with one drachm of
fal-ammoniac, difengage alkaline gas. Buc-
quet, who diftilled this mixture in the
pneumato-chemical apparatus, with mer-
cury, obtained fifty-four cubic inches of an
aeriform fluid, half of which was alkaline
gas, and the other half inflammable gas.
Four ounces of the fame filings, and two
ounces of fal-ammoniac, diftilled in the re-
tort with the common receiver, afforded
about two drachms of alkaline fpirit, con-
taining a fmall quantity of iron, which was
foon after depofited in the form of ochre;
the refidue of thefe operations was martial
muriate. The decompofition of fal-ammo-
niac by iron, is a confequence of the facility
with which this metal unites with the mu-
riatic acid, which is proved by the dif-
engagement of inflammable gas obferved
in this experiment. A fait is prepared for
medical ufes, with fal-ammoniac and iron,
which is called martial flowers of fal-am-
moniac, or ens martis. One pound of fal-
ammoniac in powder, and one ounce of iron
filings are mixed together. The mixture is
expofed in an earthen veflel, covered with a
veffel of the fame kind, to a heat capable of
igniting the lower part of the apparatus :
in five or fix hours a yellow matter is fub-
limed, which is preferved in a bottle ; this

is

284 IRON.

is the martial flowers, and confifts moftly
of fal-ammoniac fublimed, with a fmall
quantity of calx of iron. As this metal
decompofes fal-ammoniac very readily, it
muft only be employed in fmall quanti-
ties, in order that the greateft part of the
fait may fublime in its proper ftate. The
portion of martial calx which is volatilized^
colours the fal-ammoniac fublimed at the
fame time.

Calx of iron decompofes this fait more rea-
dily than the metal itfelf, fince it difengages
the volatile alkali in the cold. The alkali ob-
tained by diftillation is very fluid and cauflic.
I have obtained volatile alkali, which made
a flight eflfervefcence with acids, by dif-
tilling fal-ammoniac with half its weight
of aperitive faffron of Mars, or martial chalk;
in this experiment the cretaceous acid dif-
engaged from the iron, unites with the vola-
tile alkali, and rendered it effervefcent.

Iron is altered by inflammable gas, but
this change, which is very fenfible with
refpedt to colour, has not been examined in
other refpecfts. The calx of iron is not de-
compofed by this gas, which has lefs affinity
with the oxyginous principle than the me-
tal has, as is proved by the decompofxtion
of water by means of fire.

Sulphur combines rapidly with iron' : a
tnixtureof iron filings and fulphurin powder,
moiftened with a fmall quantity of water,
becomes hot in a few hours, at which time

it

IRON. 285

it fwells up, its parts adhere together, it
abforbs the water, breaks with a percep-
tible noife or crackling, and emits aqueous
vapours, attended with a very manifeft he-
patic odour, flightly refembling that of in-
flammable gas. If the mixture be made in
a large quantity, it takes fire in twenty-four
or thirty hours, as foon as the aqueous
vapours have ceafed. Towards the end of
the action of thefe fubftances on each other,
the heat becomes greater and greater, and is
quickly fucceeded by the inflammation ; the
fmell is then much ftronger, and appears to
arife from the inflammable gas produced by
the re-adlion of the fulphur and the iron
on the water. This fmell is a mixture of that
of liver of fulphur and of pure inflammable
air, and is doubtlefs owing to the large quan-
tity of this gas which is difengaged, that
the inflammation is due; for the flame is
much more lively than that of fulphur, and
it rifes to a foot in height, according to the
report of M. Baume, who obferved this
phenomenon with a mixture of an hundred
pounds of filings, and as much fulphur
in powder, did not laft longer than two or
three minutes 5 but the mixture remained
red hot for forty hours. M. Baume ex-
plains this inflammation, by the difengage-
ment of the phlogifton of the fulphur, in
the form of fire fet at liberty. Lemery
the elder gave the name of artificial volcano

to

286 IRON.

to this experiment, and imagined that the
fires which burn in the interior part of our
globe, and by railing the furface produce
earthquakes and volcanoes, were owing to a
iimilar combuftion of pyrites in large maffes
moiftened. Thefe terrible effefts may be
Imitated, according to the fame chemift, by
burying in the earth a mixture of fulphur
in powder, and filings of iron reduced into
a pafte, with water, and covering it up with
earth ftrongly rammed down. The experi-
ment however did not fucceed with Bucquet,
who repeated it with great exadtnefsj and the
reafon may be eafily deduced, from the ex-
periments of Prieftley. This philofopher
obferved, that a mixture of iron and ful-
phur, when moiftened, abforbed a certain
quantity of air, which doubtlefs is neceffary
for this inflammation; and the latter fa<ft
agrees very well with the theory of M.Lavoi-
fier, refpedting the decompofition of water.
In facfl it appears, the iron which is greatly
divided, re-ads on the fluid, feizes its oxy-
ginous principle by which it is calcined,
and fuffers the inflammable gas to be difen-
gaged, which takes the elaflic form, by
reafon of the heat feparated from the water :
the gas likewife diflblves a portion of the
fulphur, and forms hepatic gas.

There is a great analogy between this
combination of iron and fulphur, by the
humid way, and the efflorefcence of pyrites,

which

IRON* 287

which afford inflammable and hepatic gafes,
when they are moiftened with water.

Sulphur combines very readily with iron
by fuiion, and produces a pyritous mafs,
difpofed in needles. As the fulphur in this
cafe greatly increafes the fufibility of iron,
that metal may be inftantly fufed by the
affiftance of the combuftible body. For this
purpofe, a fmall bar of iron, heated to white-
nefs, may be applied to a roll of fulphur,
and the melted matter which drops, may be
received in a veffel of water ; it is found to
confift of blackifh brittle globules, fimilar
to pyrites, and like them formed of fmall
(lender pyramids, converging to a centre.

Iron combined with arfenic, affords a
brittle alloy, very little; known.

With cobalt it conftitutes a mixed metal,
clofe-grained, hard, and difficult to break.

It does not appear capable of uniting with
bifmuth.

Combined with regulus of antimony, it
forms a hard alloy, with fmall facets, which
fcarcely yields to the hammer. Iron has a
ftronger affinity with fulphur than with this
regulus, and confequently is capable of de-
compofing antimony. To efted: this, five
ounces of the points of horie-fhoe nails are
heated red hot in a crucible; a pound of pul-
verized antimony is then thrown in, and a
ftrongheat fuddenly given to melt the mix-
ture: whenitiswellfufed,an ounceofnitrein

powder

288 IRON.

powder is added, to affift the fufion, and fa*
cilitate the reparation of the fcoriag from the
regulus. The mixture being fuffered to cool,
a regulus of antimony is found in the cru-
cible, which does not contain iron ; but if
one part of iron be ufed with two of anti-
mony, the regulus will be martial. The fco-
riae, which are found above this laft re-
gulus, prepared with nitre' and tartar, have
a yellowtfh colour, fimilar to that of amber,
produced by the iron they contain, whence
Stahl called them fuccinated fcoriae. He di-
rects them to be reduced into powder, and
boiled in water, which takes up the moft
fubtle part of the powder ; after which the
fluid mud be decanted off, filtered, and the
powder on the filter detonated three times
with nitre : this being wafhed and dried, is
Stahl's aperitive and antimoniated faffron of
Mars.

It is ftill uncertain whether zink be ca-
pable of uniting with iron. Malouin, in
his memoir on zink, publiflied among thofe
of the Academy for the year 1742, has
fhewn, that this femi-metal may be ap-
plied, like tin, to the furface of iron, for
the purpofe of defending it from the con-
ta<ft of air, a circumftance which fhews,
that thefe two metallic matters are capable
of combining.

It feems that nickel is capable of being
very intimately united with iron, fince thefe

two

IRON. 289

two metallic fubftances can never be per-
fectly feparated, as Bergman has demon-
ftrated.

Mercury does not contract any union
with iron in its metallic ftate ; it has in
vain been attempted to unite thefe two me-
tals immediately, but the combination is
fuccefsfully made by prefenting them to
each other in the ftate of calx. Navier has
obferved, that a whitiuh fnowy precipitate
is obtained, by mixing a folution of iron
and of mercury by the vitriolic acid, and
evaporating the mixture ; in this operation
fmall flat cryftals, fimilar to thofe of feda-
tive fait, are formed. Navier affirms, that
thefe cryftals are a combination of iron and
of mercury.

Lead is not capable of uniting with iron.

Iron and tin appear fufceptible of union
by fufion. The preparation of white iron,
or, as it is commonly called, tin, which
confiits of of iron plates covered with a
thin ftratum of tin, fhews that this com-
bination takes place. In order to tin iron,
it is neceffary that the furface of the
metal fhould be very clear and bright : for
that purpofe it is corroded by an acid, or
fometimes filed or fcraped, or covered with
a folution offal-ammoniac -> it is afterwards
plunged vertically into a veffel of melted
tin ; moved backwards and forwards, to
increafe the contaft, and when fufficient-

Vol. III. T ly

29O IRON.

ly tinned, it is taken out and rubbed with
faw-duft, or bran, to clear off the fat or
pitch with which the melted tin was co-
vered, and which adheres to the furface of
the tinned iron. If iron reduced into very
thin laminas, be tinned, the tin will not
only apply to the furface, but will penetrate
into its internal parts, and the combination
will be perfect throughout, fo that when it
is cut, the fame white colour will be ob-
ferved in the middle as at its furfoce, acir-
cumftance which (hews, that well made tin-
plate is a true chemical combination ; it is
belides more malleable than iron, and is
wrought into veffels of fuch forms, as it
would be impoffible to give to pure iron by
the hammer.

The ufes of iron are fo great and exten-
five, and befides fo well known, that it
would be ufelefs to attempt to enumerate
them : it is only neceffary to obferve, that
no art can be carried on without it, and
that it is the foul of all the arts, as Mac-
quer obferves. The different modifications
it is fufceptible of, render it very pro-
per for the multiplicity of purpofes to which
it is applied. Caft iron ferves to form uten-
fils of various degrees of folidity as may be
required. The hardnefs and tenacity of the
feveral kinds of forged iron are nolefs appli-
cable to other ufes. The fame obfervation
is applicable to fteel : the finenefs of the

grain,

IRON. Zgi

gfain, and excellence of the temper, confti-
tute a great number of fpecies, peculiarly
adapted to an almoft infinite number of arts.
The calces of iron ferve to give a red or
brown colour to porcelain, enamel, pot-
tery, &c. they are likewife ufed in the pre-
paration of artificial precious ftones, and
combined with oil for painters. Iron is the
balls of an important medicine, which is fre-
quently applied with the greateit fuccefs.
It is the only metal which is not noxious,
and whofe effects are not to be feared -, it
has, even as we have feen, fuch an analogy
with organic matters, that it feems to form
part of them, and often owes its produc-
tion to the procelTes of life or vegetation.
The effedts of iron on the animal economy
are numerous ; it (Simulates the membranes
of the vifcera, and appears to ad: more espe-
cially on thofe of the mufcles, which it
braces ; it fortifies the nerves, and gives
a remarkable degree of force and vigour to
the animal fyftem ; it excites many fe-
cretions, efpecially the urinary and men-
ftrual evacuations ; it increafes the con-
tractions of the heart, and confequently ren-
ders the pulfe ftronger and quicker. Its
aftion is not lefs effectual on the fluids; it
paffes quickly through the fir ft pafTages, and
combines with the blood, to which it gives
denfity, confidence, and colour, rendering
it more concrefcible, communicating at tl\e
T 2 fame

292 IRON.

fame time fuch a degree of activity, as en-
ables it to pafs eafily into the fmalleft vef-
fels, which it Stimulates at the fame time,
and communicates force and life through
every part. The capital experiments of M.
Menghini, publimed in the Memoirs of the
Institution of Boulogne, have proved, that
the blood of perfons, who take martial me-
dicines, is higher coloured, and contains
a larger quantity of iron than it would
naturally contain. Lorry, who exercifes
the art of medicine with that accuracy of
obfervation which characterizes the true
philofopher and phyfician, obferved, that
the urine of a patient to wThom he had given
iron, in a very divided ftate, became mani-
festly coloured with nut-gall. This medi-
cine is therefore tonic, fortifying, Stomachic,
diuretic, alterative, incifive, and unites in its
action the properties of a great number of
other medicines. Like aftringents, it in-
creafes the motion of the parts, and has the
advantage of being more conftant and du-
rable in its effects than many other reme-
dies which poffefs the fame virtue, be-
caufe it combines with the organs them-
felves, by means of the fluids which ferve
for their nutrition. It feems therefore, that
in every cafe wherein the fibres of the vif-
cera, of the mufcles, or even of the nerves,
have only a very feeble action, in languors of
the Stomach, and fluggiihnefs of the intef-

tines,

IRON. 293

tines, and in weaknefles produced by thefe
caufes ; in fine, in all the cafes wherein the
fluids are not iufficiently confiftent, or too
much diluted, as in palfies and propeniities
to the dropfy, &c. martial medicines may
be adminiftered with fuccefs. It is ufed
under many different forms, fuch as the
levigated filings, martial ethiops, aftrin-
gent and aperitive faffron of Mars, martial
alkaline tin&ure of Stahl, the martial flow-
ers offal-ammoniac, &c. to thefe we may
perhaps add, iron precipitated by an acid, and
re-diflblved by volatile alkali; the Prufiian
blue propofed by the chemifts of the Aca-
demy of Dijon, &c. Martial vitriol is ex-
ternally ufed in hemorrhages, &c.

Iron pofleffing the magnetic property, or
the artificial magnet, is faid to produce very
Angular effects on theanimal economy : whea
applied to the fkin, it mitigates pain, dimi-
nishes convulfions, excites rednefs, fweat,
and often a fmall eruption ; it feems like-
wife to render epileptic fits lefs frequent;
it is affirmed, that by being left twelve hours
in water, it communicates a purgative pro-
perty to that fluid. Though all thefe effedls
require to be confirmed by repeated expe-
riments, yet it cannot be doubted, but that
the magnet has very fenfible virtues. M.
Thouret, phyfician of the faculty at Paris,
and of the Royal Society of Medicine, has
communicated in the firft volume of the
T 3 Hiftory

294 IRON.

Hiftory of the laft mentioned Society, a
valuable obfervation relative to this fubjeft,
A patient at Rouen removed a fixed pain into
different branches of the feventh pair of
nerves which are fpread on the face, by ap^
plying a loadftone to the different parts of
this region ; the fkin feemed to rife to the
magnet. There is no doubt but new obfer-
vations will offer themfelves in fupport of
thefe difcoveries, and enlighten a part of
natural philofophy, which certain perfons
have endeavoured to render more intereft-
ing, by affedling concealment.*

CHAP. XVIIL

Concerning Copper,

COPPER is an imperfect metal, of a
red brilliant colour, to which the al-
chemifts have given the name of Venus, on
account of the facility with which it unites
to, and becomes changed by, a great number
of bodies. It has a difagreeable fmell, which
is more fenfible when it is rubbed or heat-
ed $ its tafte is ftyptic and naufeous, though
lefs perceptible than that of iron ; it is hard,

* The furprifing effects of a certain piece of mummery,
which its pra£tioners called animal magnetifm, and which
engrofled much of the attention of the inhabitants of Paris
a few years ago, has been proved by the commiflioners of
the Royal Academy, to depend merely on the imagination
of the patient. See L'Hiftorie de 1' Academie Royale des,
Sciences 1784, pag. 11. Note of the Tranflator.

elaflic,

COPPER. 295

elaftic, and fonorous, very du&ile, and capa-
ble of being reduced into exceedingly thin
leaves, or fine wire ; by immerfion in water
it lofes between one eighth and one ninth of
its weight ; its tenacity is fuch, that a cop-
per wire of the tenth of an inch in diame-
ter, can fuftain a weight of 299 $ pounds be-
fore it breaks ; its fradture appears com-
pofed of fmall grains ; it is fufceptible of a
regular form -, the Abbe Mongez defcribes
its cryftals as quadrangular pyramids, fome-
times folid, and fometimes compofed of
other fimilar fmall pyramids, laterally ad-
hering.

Copper is found in the earth in various
ftates ; its ores are very numerous, but may
all be referred to the following.

1. Native copper having the red colour,
the malleability, and all the other properties
of this metal. It is diftinguifhed into two
kinds, copper of the firft formation, and
copper of the fecond formation, or of ce-
mentation. The copper of the firft for-
mation is difperfed in laminae, or fibres, in
a gangue almoft always quartzofe ; fome of
its cryftals refemble a kind of vegetation,
other fpecimens are in marTes or grains.
Copper of cementation is commonly in
grains, or fuperficial lamina?, on (tones or on
iron : this laft appears to have been depo-
sited in waters, containing vitriol of copper
which has been precipitated by iron. Na-
tive copper is found in many parts of
T 4 Europe j

296 COPPER.

Europe ; at St. Bell, in Lyons ; at Norberg^
in Sweden; at Newfol, in Hungary; and in
feveral parts of America.*

2 Copper mineralized by the cretaceous
acid : there are feveral varieties of this ore.

A. Red copper, or hepatic ore of copper.
This ore is known by its red dufky colour,
fimilar to that of the fcales which are de-
tached by the hammer from red hot copper.
M. Monnet confiders this ore as native calx
of copper; it is ufually mixed with native
copper and mountain green ; it is rare, and
fometimes cryftallized in octahedrons, or
filky fibres, called flowers of copper.

B. Earthy copper, mountain green, or
green chryfocolla. This ore is a true ochre
of copper, of a more or lefs deep green, not
heavy, and unequally diftributed on its
gangue : it appears to be combined with the
cretaceous acid, according to the analyfis
made by the Abbe Fontana of the malachite.
It is fometimes very pure, and is diftin-
guiihable into three ftates.

Simple mountain green, earthy or impure,
called likewife green chryfocolla.

Cryftallized mountain green, or filky cop-
per ore of China; this ore, which is common
in the Hartz, is likewife found in China ;
it is very pure, and cryftallized in long filky
bundles, of considerable folidity.

* And in various places in England, Scotland, and Wales. T,

Mountain

COPPER. 297

Mountain green in ftala&ites, or mala-
chite; this fubftance is found frequently
in Siberia, is convoofed of beds which re-
prefent nipples of various magnitudes -, fome
fpecimens are compofed of nredles, converg-
ing towards a common centre j the different
layers have not the fame fhades of green.
The grain of malachite is fufriciently hard to
receive a good polifh, and is therefore work-
ed into different toys ; but as it is frequently
porous, and full of unequal cavities, the folid
pieces of a certain fize are reckoned valuable.

To thefe three dates we may add a beau-
tiful green land, brought by M. Dombey
from Peru, which appears to be a calx of
this metal, mixed with land, and containing
a fmall quantity of muriatic acid, as I found
by analyiing it.

C. Mountain blue, or blue chryfocolla.
It is a calx of copper, of a deep blue co-
lour, fometimes regularly formed in rhom-
boidal prifmatic cryftals of a fine blue ; it
is then called azure of copper. At other
times it has the form of fmall grains, dif-
pofed in a cavity of different gangues, efpe-
cially quartz ; it ufually conftitutes fuper-
ficial layers in the cavities of the grey and
yellow copper ores. All thefe calces of
copper appear to have been precipitated
from vitriolic folutions of copper, by the
intermedium of calcareous earths through
which the waters have tranfuded. Mr. Sage
confiders thefe blue copper ores as combina-
tions

298 COPPER.

tions of copper with the volatile alkali,
from which he affirms they differ only in
their lefs degree of folubility ; he like wife
thinks that the malachites is produced from
this blue, which he calls tranfparent azure
copper ore; but the greater number of mine-
ralogifts have not adopted this opinion. M.
De Morveau thinks that blue calx of cop-
per does not differ from the green calx, but
in the circumftance of its being lefs cal-
cined.

The blue calx of copper colours certain
ftones, more efpecially turquois ftone, in
which Reaumur found copper, and the
lapis armenius, whofe bafe is calcareous
earth, or gypfum. Mr. Kir wan reckons
thefe blue ftones as a fpecies of copper
ore. The Turquois ftone is formed of the
bones of animals, coloured by copper ; thofe
of Pruffia are not attacked by the nitrous
acid, according to Reaumur; but thofe of
Languedoc are completely foluble in that
menftruum.

3. Copper mineralized by the muriatic
acid, and united to clay. Mr. Werner fpeaks
of this ore in his tranflation of Cronftedt ;
it has been confounded with talc, and a perfon
of the name of Dans expofed it to fale at Pa-,
ris in the year 1784, under the name of green
mica ; it confifts of final] beautifully green
cryftals, or fmall brilliant fcales. Mr. Fof-
ter difcovered it in the mines of John Geor-

genftadt x

COPPER. 299

genftadt ; the green cupreous fand of Peru
already mentioned, is perhaps referable to
this ore.

4. Copper mineralized by fulphur, with
fcarcely any heat : this is called by the very
improper name of vitreous copper ore; it is
of a deep violet grey, greenifh brown, or
liver colour; it melts by a very gentle heat,
is ponderous, fometimes flexible, and always
yields to the knife ; in its fradture it appears
brilliant like gold; it is one of the richeft
ores of copper, as it affords about ninety
pounds of metal per hundred weight.

5. Copper mineralized by fulphur, with
more iron than the foregoing ; azure copper
ore ; it does not differ from the preceding,
but in the quantity of iron, which fome-
times amounts to thirty pounds per quintal;
it affords no more than fifty or fixty pounds
of copper per quintal, the reft being fulphur:
thefe two ores are conveniently afl'ayed by
acids.

6. Copper mineralized by fulphur, with
much iron; brilliant or yellow pyrites. The
quantity of fulphur and copper varies great-
ly in this mineral, the iron is always very
abundant. It forms veins in the earth.
This ore is fometimes mafiy, and of a dark
colour; it often appears fcaly, and as it
were micaceous ; in this form it is found
in Denmark, Norway, Sweden, and St.
Marie aux Mines, in France. Sometimes
it is diffeminated in its gangue, like the

copper

COPPER.

; this variety is often mix-
quantity of azure. The cu-
i often prefent very brilliant
colours at their furface, which
by the decompofition of their
principles : they are then called chatoyant
ores of copper, or ores refemblirig the pea-
cock's tail ; they commonly contain a large
quantity of fulphur, a fmall quantity of iron,
and are not rich in copper ; fuch are the
ore? of Derbyshire, in England; fome of
thofe of St. Bell, in Lyons, and many ores
of Alfatia, fuch as thofe of Caulenbach and
Feldens; they adhere to every kind of
gangue, rock cryftal, quartzofe ipar, fchiflus,
mica, &c.

7. Copper united to fulphur, arfenic,
iron, and a fmall quantity of filver. This,
ore, called arfenical copper ore, or fahlerts,
greatly refembles the grey filver ore, being
only fomewhatlefs brilliant, and differs mere-
ly from that, in containing a lefs quantity
of filver. M. Rome de Lille likewife dif-
tinguifhes a white copper ore, which con-
tains, according to him, rather more filver
than the grey, but it is in reality a filver ore.
The fahlerts commonly affords from thirty-
five to fixty pounds per quintal.

8. Copper mineralized by fulphur and
arfenic, with zink and iron ; brown or
bledofe copper ore. M. Monnet found
this ore only at Catherineberg, in Bohemia ;

it

COPPER. 301

it is brown, granulated, and very hard, and
contains from eighteen to thirty pounds of
copper per quintal.

9. Schiftofe copper ore. This confifts of
the vitreous copper ore, very intimately
mixed in a brown or black fhiftus. It con-
tains from fix to ten pounds per quintal ;
chalk muil: be added in order to fufe it.

10. Bituminous copper ore. This con-
fifts of copper ore mixed with a kind of
pitcoal, in Sweden.

1 1 . Black copper ore, of the colour of
pitch. Mr. Gellert denominates it copper
ore in fcoriae ; it is a refidue of the decom-
position of the yellow and grey copper ores,
which contain neither fulphur nor arfenic,
and approaches to the ftate of malachite ; it
has a black mining appearance like pitch.

12. Copper united to fulphur and arfe-
nic, containing antimony: antimonial cop-
per ore. Mr. Sage mentions this ore in
his Elements of Mineralogy; it is grey and
brilliant in its fracture, like antimony, and
contains from fourteen to twenty pounds
of copper in the quintal.

To affay an ore of copper, it muft firft be
pounded and warned, and then roal'ted for a
long time by a ftrong heat, and laftly, melt-
ed with four times its weight of black flux
and marine fait; the button, which is often
rendered black by a remaining portion of ful-
phur, muft be melted with four parts of lead,

and

302 COPPER.

and cupelled, in order to feparate the filver
and gold it may contain ; becaufe there are
few copper ores which do not contain a
certain quantity of thefe precious metals.
The flux of Mr. Tillet, which is a mixture
of two parts of pounded glafs, with one of
calcined borax, and one eighth of charcoal,
fucceeds better for thefe reductions, than
the black flux, becaufe the latter forms a
hepar, which diflblves part of the calx of
copper.

Bergman advifes the application of the
vitriolic and nitrous acid, in the affay of
thefe ores by the humid way; when the
copper is diflblved by the acids, it is pre-
cipitated by iron.

In the large way copper ores are pound-
ed, warned, and roafted in the open air, with
fcarcely any additional fuel, becaufe the
fulphur they contain burns of itfelf, as
foon as it is well fet on fire. When it is
burnt out, the ore is roafted once or twice
more with wood, and is melted in an open
fire, into the fubftance called a mat of
copper ; the mat confifts of copper which
ftill contains a portion of fulphur : the fu-
fions it is fubje&ed to, ferves to prefent new
furfaces of the metal to the air, in order
that it may be roafted with greater facility.
After fix or feven fuccefiive roaftings, ac-
cording to the quantity of copper the ore
may contain, it is at laft fufed into black

copper,

/

COPPER. 303

copper, which though malleable, flill contains
a portion of fulphur, which is not feparatcd,
but by the procefs for the extraction of the
perfeft metals it contains. The black copper
is fuied with three times its weight of lead,
which is called refreming the copper, and
this mixture is cafl in moulds, into the form
of loaves, called loaves of eliquation. Thefe
are placed on two plates of iron, inclined in
fuch a manner as to leave an opening be-
tween them at the bottom ; the plates com-
pofe the upper part of the furnace of eli-
quation, whofe bottom flopes forward ; the
fire made beneath the plates, heats the
loaves; the lead melts and flows down among
the coals, carrying with it the filver and the
gold, with which it has a ftronger affinity
than the copper. After this operation,
which is termed eliquation, the loaves are
found coniiderably diminifhed in weight,
and changed in figure; the heat is then
railed, fo that the copper may be nearly
melted, in order that all the lead may be
perfe&ly feparated. The lead containing the
perfect metals is carried to the cupelling
furnace; and the copper is refined by melting
in a crucible, where it remains a fufficient
time to throw up, in the form of fcoria?, all
foreign fubftances it may contain; it is
examined from time to time, by immerfing
iron rods in it, which become coloured with a

fmall

304 COPPER.

fmall quantity of copper, and its purity is
judged by the brilliant rednefs of thefe fpe-
cimens. Refined copper is caft into plates,
or into rofettes -, to form a rofette, the
fcorias which cover the copper in fufion,
are carefully removed, and the furface of the
metal is fuffered to congeal. When it is no
longer fluid, a wet broom is applied, the
cold caufes it to fhrink, and a congealed
portion of the metal not only detaches it-
felf from the fides of the crucible, but from
the reft of the melted metal, from which it is
taken with tongs ; the greateft part of the
copper is, by repeating this operation, con-
verted into rofettes ; the portion which re-
mains at the bottom is called the king.

Cupreous pyrites, which contain but a
fmall portion of metal, are not worked but
for the purpofe of extracting fulphur and
vitriol. At St. Bell, and in many other places
they are roafted, and expofed to diftillation,
to feparate the fulphur. During the roafting,
a portion of the vitriolic acid re-adts on the
metal, diflblves it, and begins to form vi-
triol. The roafted pyrites are afterwards
expofed to the air. When the vitriolization
is finifhed, the pyrites are lixiviated, and by
evaporation of the filtered liquor, a fait, in
blue rhomboidal cryftals, called cupreous
vitriol, blue vitriol, blue copperas, or Cy-
prian vitriol, is obtained. We mall fpeak

of

COPPER. 305

of this fait among the combinations of this
metal.

Copper when heated, becomes coloured
on its furface, nearly in the fame manner as
fteel ; the colours are blue, yellow, and laft-
ly, violet ; it does not melt till it is ftrongly
ignited ; when completely fufed, it appears
covered with a green flame, boils, and is
volatilized, as may be obferved in thechim-
nies of foundries. Flowers of copper are
likewife found in the melting pots. If this
metal be projected through flame, in fmall
filings, it produces a blue and green colour,
and from that property it is ufed in fire-
works. If the melted metal be fuffered to
cool flowly, and, after the furface is become
congealed, the fluid portion be poured off,
the remaining folid part is found to be cry-
flallized in pyramids; which are more regu-
lar and large, in proportion as the fufion
has been more complete, and the cooling
more gradual : its pyramids are quadran-
gular, and appear to be formed of a great
number of o&ahedrons, inferted one in the
other.

Copper heated with accefs of air, burns
at its furface, and is converted into a calx
of a dark red, in proportion as it abforbs the
bafe of vital air: this calx maybe eafily ob-
tained by heating a ball of copper to red-
nefs, which caufes the calx to fcale off".
The fame effeft takes place, when red hot
Vol, III. U copper

306 COPPER.

copper is quenched in cold water ; the fud-
den contraction of the parts of the metal,
facilitating the feparation of the portion of
calx which covers the furface : this calx
falls to the bottom of the water, and is cal-
led fcales of copper. As it is not perfectly
burnt, it may be calcined afrefli in the muf-
fel of the cupelling furnace ; after which
laft procefs it is found to be of a deep brown
colour; but by a violent heat it melts into a
mafs of a blackifh or deep reddifh brown
colour. The calx of copper may be decom-
pofed, and deprived of the bafe of air, which
alters its metallic properties by oils, refins,
&c. The fcorias are partly reducible without
addition, for the founders, who buy them of
the copperfmiths, take no other trouble with
them, than that of throwing them into large
crucibles on the melted copper, with which
they incorporate by fufion ; the fame me-
thod is ufed to melt the filings. The calx
of copper appears to pofiefs fome faline pro-
perties, but its nature has not yet been as-
certained.

The air attacks copper with greater or lefs
facility, accordingly as the fluid is more or
lefs loaded with moifture, and converts it
into a rufl, or green calx, which appears to
have fome faline qualities, viz. tafte and
folubility in water. From this circum-
ftance the ancient chemifts admitted the
exiftence of a fait of copper. It is remark-
able,

COPPER. 307

able, that this ruft never attacks copper, ex-
cept at the furface, and feems even to con-
tribute to the prefervation of the internal
parts and mafTes of this meta!, as may be
feen in antique medals and ftatues, which
are preferved very well beneath a covering of
ruft. The antiquarians call this cruft pati-
na, and fet a high value on it, becaufe it
fhews the antiquity of the pieces which are
covered with it. Many artifts, and in par-
ticular the Italians, know how to imitate
this coating, and to counterfeit the antique
bronzes.

The calcination of copper by humid air,
appears to be produced by water in the
ftate of extreme divifion \ this fluid how-
ever does not appear to attack copper, nor
decompofe it like iron, at a high tempera-
ture. This metal feems to be more calci-
nable by cold water; it being a well known
fadt, that more danger attends the fuffering
of fluids to cool in copper veiTels, than in
making them boil : becaufe, as long as the
fluid is boiling, and the veflel hot, the aque-
ous vapour does not adhere to its furface ;
but when the veflel is cold, the drops of*
water which adhere to its tides, calcine it,
and reduce it into green calx. The air and
the cretaceous acid diftributed therein, con-
tribute, doubtlefs, greatly to this calcina-
tion ; for by diftilling this ruft of copper
U 2 in

308 COPPER.

in the pneumato-chemical apparatus, I have
obtained cretaceous acid.

Copper does not unite with earthy mat-
ters ; its calx facilitates their fufion, and
forms with them glaffes of a deep brown.

Ponderous earth, magnefia, and lime, have
no evident action on copper, and the adlion
of thefe fubftances on the calces of that
metal, is not known.

Cauftic fixed alkalies digefted in the cold
with copper filings aflume, at the end of a
certain time, a light blue colour, the cop-
per becoming covered with a powder of the
fame colour ; thefe folutions are better ef-
fected in the cold than by the afiiftance of
heat, according to Monnet. It is neverthe-
lefs eflential to be obfefved, that this che-
mift made ufe of cretaceous vegetable alka-
li, inftead of pure fixed alkali, which laft
appears to have a much ftronger adlion on
copper.

The volatile alkali diffolves this metal
much more rapidly. The filings of cop-
per digefted with this fait, produce at the
end of a few hours, a deep and moft beau-
tiful blue; the quantity of copper taken up
is very inconfiderable. I have obferved the
phenomena of this folution for the fpace of
a year in a fmall bottle. Cauftic volatile
alkali was poured on filings of copper -, at
the end of feveral months the furface of
the metal was covered with a blue calx;

the

COPPER. 309

the fides of the bottle were covered with a
calx of a pale blue, and the lower part of
the bottle which contained the copper, ex-
hibited on the furface of the glafs a brown
calx, whofe upper part was yellowifh : this
liquor lofes its colour almoft entirely when
kept clofe, but it re-appears again when
the bottle is opened. This phenomenon
does not appear in a very evident manner,
excepting at firft, and when the folution is
decanted from the copper ; if the folution
be old, and the copper ftill remains in it,
its colour is of "a beautiful blue, though
in clofed veflel's ; but on expofure to air it
becomes deeper. By flowly evaporating
this folution in the fire, greateft part of
the volatile alkali is diffipated, the portion
remains fixed with the calx of the metal,
and is depofited in the form of foft cry-
ftals, as -Monnet has obferved. Mr. Sage
affirms, that very beautiful cryftals may be
obtained by a flow evaporation, and has
compared#them to the natural azure of cop-
per. The latter fubftance does not however
afford volatile alkali when heated ; is in-
foluble in water, and does not efHorefce in
the air like that prepared by art. M. Baume
affirms, that this compound affords very
brilliant cryftals, of a beautiful blue. The
folution expofed to the air dries quickly,
and leaves a grafs green fubftance, which
is merely a calx of copper. Mr. Sage

U 3 thinks

3IO COPPER.

thinks that malachite is thus produced.
But this calx does not afford cretaceous acid,
as the earthy ore of copper does. If an acid
be poured into the folution of copper by
the volatile alkali, no precipitate is formed,
but the blue colour difappears totally, and
becomes converted into a very pale green.
This phenomenon, which has been obferv-
ed by Merfrs. Pott and Monnet, fhews that
the quantity of calx of copper in volatile
alkali is very fmall, and that it is re-dif-
folved by the acid, or by the ammoniacal
fait, formed by the addition of the acid. The
blue colour may however be made to appear
again, by the addition of volatile alkali to
the mixture. The calx of copper formed
by fire, and every other calx of this metal,
diffolves immediately in pure volatile alkali,
-which by this means may be made to take
up a good quantity of the metal, a moft
beautiful colour being at the fame time
produced. From this property the volatile
alkali has been propofed, as a teft to difco^
ver the fmalleft portion of copper in all
matters in which its exiftence may be fiif-
pefted.

The vitriolic acid does not adl on copper
but when concentrated and boiling; much
fulphureous gas is difengaged during the fo*-
lution. A brown matter, of the confiftence
of a thick fluid, containing calx of copper,
and a portion of the calx combined with

the

COPPER, 3II

the vitriolic acid, are found at the bottom;
from which, by the addition of water and
filtration, a blue folution is obtained : if
this be evaporated to a certain point, and
fufFered to cool, rhomboidal long cryftals
are afforded, of a beautiful blue colour,
called vitriol of copper: if the folution, in-
ftead of being evaporated, be left expofed
a long time to the air, it affords cryftals ;
but a green calx is precipitated. All the
calces of copper when formed or dried in
the air, are of this colour.

Vitriol of copper has a very ftrong ftyptic
tafte, approaching even to caufticity ; when
expofed to heat it very foon melts, lofes its
water of cryftallization, and becomes of a
blueifh white ; a ftrong heat is required to
feparate the vitriolic acid, which adheres
much more ftrongly to the calx of copper
than to that of iron. Vitriol of copper is
decompofed by magnefia and by lime ; the
precipitate formed by either of thefe fub-
ftances, is of a blueifh white, but becomes
green if dried by expofure to air. Hence
fome chemifts affirm, that the precipitates
of vitriol of copper are green : the fame is
true of the precipitates obtained by fixed
alkalies in the different ftates ; being firfl:
blueifh, and affuming a green colour as
they dry. Mountain green may perhaps be
formed in this manner. We muft obferve,
that when vitriol of copper is precipitated
U 4 by

312 COPPER.

by the folution of cretaceous vegetable al-
kali, no effervefcence is excited, which is a
proof that the cretaceous" acid unites readily
with the calx of copper. All metallic fo-
lutions do not exhibit this phenomenon.
Volatile alkali precipitates the folution of
vitriol of copper in the fame manner, of a
blueifli white colour; but the mixture very
foon affumes a deep blue colour, becaufe
the volatile alkali diflblves the precipi-
tate. A very fmall quantity of this fait
is fufficient to re-diffolve all the calx of
copper feparated from the vitriolic acid.

The nitrous acid diflblves copper with
great rapidity in the cold ; a large quantity
of very red nitrous gas being at the fame
time difengaged. This is the method ufed
by Dr. Prieftley, to obtain a very flrong
nitrous gas. A portion of the metal re-
duced to the (late of calx, is precipitated in
the form of a brown powder, and is fepa-
rated by the filter. The filtrated folution
is of a much deeper blue than the vitriolic
folution, which (hews that the copper is
more perfectly calcined ; by previous and
careful evaporation, cryftals may be obtain-
ed in cooling. Macquer is one of the firft
chemifts who obferved this property, in
his Memoir on the folubility of falts in
fpirit of wine. If its cryftals be formed
very (lowly, they have the figure of long
parallelograms \ if more quickly depofi ted,

they

COPPER. 313

they are hexahedral prifms, with an obtufe
point, irregularly difpofed, and refembling
bundles of divergent needles. Laftly, if
this folution be too much evaporated, it af-
fords only a magma, of an irregular form :
which doubtlefs occafioned certain chemifts
to affert, that the folution was not fufcep-
tible of cryftallization. Cupreous nitre is
of a very bright blue, and is fo cauftic, that
it may be employed in corroding the ex-
crefcences which arife on the fkin ; it melts,
according to Mr. Sage, at the temperature
of twenty degrees of the thermometer of
Reaumur, and detonates on burning coals,
though this phenomenon is fcarcely fen-
fible, on account of the large quantity of
water it contains. When melted in a cru-
cible it emits large quantities of nitrous va-
pour, which may be collected by diftilla-
tion; when dried, its colour is green; an
increafe of the heat converts it to a brown,
in which ftate it is merely a calx of copper.
I have diftilled this fait with the pneumato-
chemical apparatus, and obtained much ni-
trous gas, a fmall quantity of cretaceous
acid, and not a particle of pure air; it was
converted into a brown calx by this opera-
tion. Nitre of copper attracts the moif-
ture of the air, but it may be preferved a
long time in clofe veffels. In a dry and
hot air it becomes covered with a green ef-
florefcence. It is very foluble in water, and

rather

314 Copper.

rather more fo in hot than in cold water.
The folution expofed to the air in fhallow
veffels, or quickly evaporated in hot and dry-
weather, leaves a calx of the fame green
colour as the cryftals of the fait have in
fimilar circumftances. It is precipitated by
lime, and is then of a pale blue colour; by
fixed alkalies of a pale blueifh white ; by
volatile alkali in flocks of the fame colour,
which are very quickly re-diflblved, and pro-
duce a brilliant deep blue colour in the
liquor ; by liver of fulphur of a reddifh
brown colour, without an hepatic fmell ;
and by tin&ure of nut-galls, of an olive
green. The vitriolic acid likewife diflblves
cupreous nitre, and blue cryftals of vitriol
are obtained, if the acid be ufed in a very
concentrated ftate. Stahl obferved this de-
compofition: M. Monnet has fince confirm*
ed it, and I have feveral times had occafion
to make the fame obfervation. Iron has a
ftronger affinity with moft acids than cop-
per. When a plate of iron is plunged in a
folution of copper by the nitrous acid, the
copper is precipitated in the metallic form,
and covers the furface of the iron ; this
precipitation depends on the ftronger affi-
nity of the iron than of the copper to the
bafe of air. The vitriol of copper exhibits
the fame phenomenon, and this procefs has
been ufed by impoftors to impofe on the
credulous.

The

COPPER. 315

The muriatic acid does not diflblve cop-
per, unlefs it be concentrated and boiling.
The quantity of gas difengaged during
this folution is but fmall, and its nature
is not known; it feems, however, to be in-
flammable gas. The muriatic acid affumes
a very deep and aim oft brown colour; the
combination forms a magma very foluble
in water; if it be lixiviated, the water be-
comes of a beautiful green colour, which
diftinguifhes this folution from the two
foregoing : when flowly and cautioufly eva-
porated, and fufFered to cool, it depofits
prifmatic cryftals of a regular form; on the
contrary, if the evaporation has been too
rapid, and the cooling too fudden, it prefents
only very fmall fharp needles.

The muriate of copper is of a very agree-
able grafs green colour, its tafte is cauftic, and
very aftringent, and it melts by a gentle heat,
congealing again into a mafs when fufFered
to cool. M. Monnet affirms, that the mu-
riatic acid adheres very ftrongly to it, and
that it cannot be volatilized, without the
affiftance of a considerable heat. It ftrone-
ly attracts the moifture of the air, and is
decompofable by the fame intermediums as
the preceding falts of copper. I have ob-
ferved, that the volatile alkali does not dif-
folve the calx of copper feparated from the
muriatic acid, fo well as that which is fepa-
rated

316 COPPER,

rated from vitriol and cupreous nitre. The
nitrous folutions of mercury and filver de-
compofe it by double affinity, a white pre-
cipitate being formed by the tranfpofition of
the muriatic acid to the mercury or to the
filver, and by the union of the calx of copper
to the nitrous acid. I have however ob-
ferved, that the liquor does not aflume a
blue colour, which the folution of copper
by the nitrous acid ought to have; and that
in general the calx of copper formed by the
muriatic acid, does not take this colour but
with difficulty, as we have already obferved
with refpect to the volatile alkali. It feems
to me, in general* that the calces of copper
pafs very eafily from blue to green, but dif-
ficultly from green to blue. The muriatic
acid difTolves the calx of copper with much
more facility than copper itfelf. This fad:
has been well obferved by Brandt. The
folution is of a fine green, and cryftallizes
as eafily as the former, which proves, that
in the faline combinations of metals, the
latter are always in the ftate of calx, as we
have already obferved.

Nitre detonates difficultly by the addition
of copper ; the fait muft be melted, and the
copper very hot, in order that the deflagra-
tion may take place ; otherwife it is very
feeble. This operation is made by throw-
ing filings of copper on nitre in fufion in a
large crucible, in order that the contact may

be

COPPER. 317

be fufficiently large. When the metal is
ftrongly heated, a. flight motion, accom-
l panied with fmall flafhes, is obferved : the
refidue is a calx of a brownifh grey, mixed
with vegetable alkali. This being wafhed,
the water feizes the alkali, which retains a
fmall quantity of copper, and the calx of
the metal remains pure. It flows without
addition into a glafs of a deep opake brown,
ufed in colouring enamels ; the alkali is
thought to be rendered cauftic, but no ex-
periments on this fubject have yet been
made with fufficient accuracy.

Copper decompofes fal-ammoniac very
readily. Bucquet, who examined this de-
compofition with great care, obtained by
the pneumato-chemical apparatus over mer-
cury, from two drachms of copper filings,
and one dram of fal-ammoniac, fifty-eight
inches of elaftic fluid, of which twenty-fix
inches confifted of very good alkaline gas,
twenty-fix of detonating inflammable gas,
and fix of mephitical gas, which extinguished
candles without being abforbed with water,
and without precipitating lime-water. The
latter gas, or atmofpheric mephitis, ap-
pears to be the producl of thedecompofition
of a fmall portion of volatile alkali. Alka-
line volatile fpirit was difengaged in a fmall
quantity, of a beautiful blue colour, which
floated above the mercury. This experi-
ment fhews us, that the muriatic acid pro-
duces

318 COPPER.

duces an inflammable gas by diflblving the
copper. The refidue was a mafs of a black-
ifh green, of which half was diffolved by the
water, and communicated to it a green co-
lour, which is a diflindtive charafter of the
muriate of copper; the other half exhibited
a kind of calx of copper, formed by the
muriatic acid. When this decompofition is
repeated in the dofe of four ounces of cop-
per with two ounces of fal-ammoniac, in
the common apparatus, Bucquet obtained
two drachms eighteen grains of blue vola-
tile alkaline fpirit, which effervefced with
acids, and contained about one cubic inch of
cretaceous acid in the dram. This chemift
was at a lofs to determine whence the latter
gas was produced, but I think it may arife
from fome impurities in the fal-ammoniac ;
for having repeated this experiment with fal-
ammoniac purified by fublimation, I obtain-
ed a very cauftic volatile alkali, which did
not at all effervefce with acids. The calx
of copper likewife decompofes fal-ammo-
niac, and affords a portion of cretaceous
acid, together with the volatile alkali it dif-
engages, which renders the latter effervef-
cent. This alkali is always blue, becaufe
it carries up with it a fmall portion of the
calx of copper, to which its colour is owing.
Acids do not however precipitate this metal.
Two medicines are prepared in pharmacy1
with fal-ammoniac and copper, of which

the

COPPER. 319

the firft has received the name of cupreous
ammoniacal flowers, or ens veneris, and is
nothing more than fal-ammoniac coloured
by a fmall portion of calx of copper. A
mixture of eight ounces of this fait, with
one drachm of the calx of copper, is fub-
limed in two earthen veflel s, the one placed
on'the other : all the fal-ammoniac is vola-
tilized without being decompofed, and car-
ries up a fmall quantity of copper, which
gives it a blueifh colour. The fecond,
which is called aqua celeftis, is prepared by
fuffering a pound of lime-water and an
ounce of fal-ammoniac to remain in a cop-
per veflel for ten or twelve hours ; the lime
difengages the volatile alkali, which dif-
folves a fmall quantity of copper of the
bafon, and produces the blue colour. The
celeftial water may be made in a glafs or
earthen veflel, if a fmall quantity of filings,
or calx of copper, be added to the lime-
water and fal-ammoniac.

Copper appears to decompofe alum ; for
if a folution of this fait be boiled in a cop-
per veflel, a fmall quantity of clay is depo-
fited; and when the alum is precipitated
by volatile alkali, its earth aflumes a flight
blue colour, denoting the prefence of cop-
per. This effect may likewife be attributed
to the fmall excefs of acid, which alum al-
ways contains.

Inflammable

320 COPPER*

Inflammable gas does not aft on copper,
but reduces its calces, by depriving them of
the bafe of vital air, with which this gas
has a ftronger affinity than the copper.

This metal unites very readily with ful-
phur ; the combination may be made in the
humid way,, that is to fay, by mixing flow-
ers of fulphur and copper filings together,
with a fmall quantity of water; but it fuc-
ceeds much better in the dry way. A
mixture of equal parts of fulphur in pow-
der and copper filings, are put into a cru-
cible, which is heated by degrees, till it be-
comes red hot; the refult is a mafs of a
blackifh grey, a fort of mat of copper, which
is brittle and more fufible than the copper
itfelf. This compound is prepared for dying
and painting on callicoes, by placing ftrata
of plates of copper and fulphur in powder in
a crucible, and heating it gradually, as we
have obferved. The kind of mat which is pro-
duced, is pulverized, and called aes veneris.
Liver of fulphur and hepatic gas have a
ftrong adlion on copper : the former dif-
folves the metal by the dry, as well as by the
humid way ; the fecond ftrongly colours
the furface, but its effeft has not yet been
well examined into.

Copper forms alloys with many metals ;
with arfenic it becomes white and brittle,
and forms white tombac j it unites with
bifmuth, and according to Gellert, forms

an

COPPER. 321

alloy of a reddifh white, with cubic fa-
cets.

It unites very readily with regulus of an-
timony, and affords a regulus, which is dif-
tingui^hed by a beautiful violet colour; it
likewife decompofes antimony, and unites
with the fulphur, which it takes from the
regulus.

It combines very readily with zink.
This combination may be made in two
ways. Firft by fufion; a metal is produced
whofe colour refembles that of gold, and
which is much lefs fufceptible of ruft than
copper, though lefs ductile than that metal :
the nearer its colour approaches to that of
gold, the more brittle it is ; and it varies
greatly according to the proportion of the
mixture, and the precautions ufed in melt-
ing it ; its varieties are fimilor, Pinchbeck,
princes-metal, Manheim gold. Secondly, by
cementing plates of copper with lapis cala-
minaris reduced to powder, and mixed with
charcoal ; in a red heat, the copper unites
with the zink, and forms brafs : this is lefs
fufceptible of ruft than copper, and is like-
wife more fufible, and lefs malleable. But
a ftrong heat continued for a (hort time, de-
prives it of the zink with which it was
united, and converts it into copper again.

Copper unites difficultly with mercury;

though a fort of amalgam may be produced,

by triturating copper in very thin leaves with

mercury. A plate of this metal plunged in

Vol. III. X a folution

322 COPPER.

a folution of mercury by the nitrous acid,
becomes coated over with the femi-metal,
precipitated by the copper.

Copper and lead unite very eafily by fu-
fion, as the formation of the leaves #f eli-
quation prove.

Copper is combined with tin in two ways,
either by applying melted tin on copper,
or melting both metals together. The firft
operation is ufed in the tinning of copper,
the fecond forms bronze. To tin copper
veflels, they are firft fcraped, in order to
render their furface clean and brilliant; after
which they are rubbed with fal-ammoniac,
to clean them more perfectly. They are
then heated, and fprinkled with powdered
refin ; this fubftance covering the fubftance
of the copper, prevents its calcination.
Laftly, the melted tin is poured on, and
fpread about. It is with juftice com-
plained, that the tinning of copper veflels
is not fufficient to defend them from the
adlion of air, moifture, and faline fub-
ftances, becaufe thefe veflels are frequently
obferved to be covered with verdigris. It
might be poflible to remedy this inconve-
nience by a thicker covering of tin, if there
were not reafon to fear, that a degree of
heat fuperior to that of boiling water, to
which thefe veflels are often expofed,
would melt the tin, and leave the furface of
the copper uncovered. To prevent this

laft

COPPER. 323

laft accident, the tin may be alloyed with
iron, iilver, or platina, to diminifh its fufi-
bility, and render it capable of being ap-
plied in thicker ftrata on the copper. Al-
loys of this kind are already ufed in ieveral
manufactures. The very fmall quantity of
tin required to cover the furface of copper,
is furprizing; MeiTrs. Bayen and Charlard
having determined, that a veffel of nine
inches in diameter, and three inches three
lines in depth, did not gain more than
twenty-one grains by tinning. This fmall
quantity is neverthelefs fufficient to prevent
the dangers which might arife from the ufe
of copper veffels, provided care be taken,
that fubilances capable of diffolving the tin
be not fuffered to remain too long a time in
the veffels; and mere efpecially that the tin
be frequently renewed: as the friction, heat,
and action of fpoons, with which the in-
cluded fubftances are furred, deftroy it very
quickly. There is likewife another caufe
of appreheniion refpecling the tin ufed by
braziers in tinning, ccc. It is often alloyed
with one fourth of its weight of lead ;
and in this cafe the bad effects of the latter
metal are much to be feared, as it is
known to be very foluble in acids and fat
fubftances. It is therefore neceffary that
government mould take fufficient care that
the braziers be not deceived in the tin they
purchafe, and that they may not employ
X 2 any

324 COPPER.

any but the Mallacca or Banca tin, in the
ftate it is received in from the Indies, with-
out having been alloyed or re-melted by the
pewterers.

M. De la Folie, citizen of Rouen, well
known by his chemical labours refpecting
the arts, and the ufeful difcoveries with
which he has enriched the arts of dying, of
pottery, and a great number of manufactures
at Rouen, propofed, in order to avoid the
inconvenience and danger of tinning copper,
that faucepans of forged iron covered with
zink, might be ufed, which, as we have al-
ready feen, is not productive of any danger-
ous effects. Many perfons have already ufed
thefe veflels, and have been fenfible of their
advantages. It is much to be defired, that
the ufe of thefe veflels may become more
general.

When tin is melted with copper, a metal
fpecifically heavier than the two metals em-
ployed, is obtained. This alloy is whiter,
more brittle, and more fonorous, in pro-
portion as the quantity of tin is greater.
When it is very white it is called bell-me-
tal ; when it contains a larger proportion of
copper, it is yellow, and is called bronze.
This laft is ufed in cafting ftatues, and
forming pieces of artillery, which require
to be fufficiently folid not to burft, and not

fo

COPPER, 32$

fo duftile as to have their form deftroyed by
the ftroke of bullets.*

Copper and iron are capable of uniting
either by fufion, or in the way of foldering;
yet this combination does net eafily fuc-
ceed. When a mixture of the two metals
is melted in a crucible, the iron is found
in pieces in the copper, without being per-
fectly united. Copper decompofes the mo-
ther water of martial vitriol, though iron
has a flronger affinity with acids than cop-
per.f

The ufes of copper are numerous, and
well known. The alloy of copper and zink
is mod commonly ufed on account of its
great ductility and its beauty. As copper
is a very violent poifon, it ought never to
be adminiflered in medicine. The proper-
eft remedies in cafe of poifoning by copper
reduced into calx or verdigris, are emetics,
abundance of water, liver of fulphur, al-
kalies, Sec.

* When the dofe of tin exceeds that of copper, the me-
tal becomes foft, but the fpecifk gravity in almoft every
proportion of the two metals, is equal to, and in fome cafes
exceeds, that of the heavier. T.

t This fact is well explained by Bergman, in his Trea-
tife on Elective Attractions, § VI.' The iron, in the mo-
ther water of martial vitriol, is dephlogifticated beyond a
certain limit; or, according to the pneumatic theory, it is
combined with a portion of the bafe of pure air. In this
ftate it attracts the acid lefs than copper does. T.

x 3 CHAP.

J26 SILVER.

CHAP. XIX.

Concerning Silver.

QlLVER, called Luna or Diana by the
^ alchemifts, is a perfect metal of a white
colour, and of the moft lively brilliancy ;
it has neither tafte nor fmell j its fpecific
gravity is fuch, that it.lofes about the ele-
venth part of its weight by immerfion in
water, and a cubic foot of this metal weighs
720 pounds. Silver is fo ducffcile, that it
may be beat into exceedingly thin leaves,
and drawn into wire much finer than a
hair.* A grain of filver may be extended fo
as to form a veflel capable of containing an
ounce of water. Its tenacity is fo confi-
derable, that a filver wire of the tenth of
an inch in diameter, may fuftain a weight
of 270 pounds without breaking. Its hard-
nefs and elafticity are not equal to thofe of
copper. It is the moft fonorous of metals
after thofe we have mentioned. It hardens
under the hammer, but very readily lofes
that hardnefs by heating. MefTrs. Tillet
and Mongez have cryftallized this metal,
and obtained quadrangular pyramids, fome-
times infulated like thofe which are found

* A grain of leaf filver meafures fomewhat more than
5 1 fquare inches, and the filver wire, ufed by aftronomers,
about the TJB of an inch in diameter. This is about half
the diameter of a fine human, hair. T,

on

SILVER. 327

on the edges of the crucibles in which this
metal has been melted," or grouped and la-
terally placed one on the other.

Silver is found in many various flates in
nature ; the principal ores of this metal
may be reduced to the following.

1. Native or virgin filver; it is known
by its brilliancy and ductility, and is found
in a great variety of forms; it is often in
irregular mafles, more or lefs confiderable
in magnitude. Sometimes it has the form
of capillary threads twifted round, and in
this ftate feems to have been produced by
the decompoiition of a red filver ore, as
Henckel and Rome de Lifle have obferved.
It is likewife found in plates and in forms,
which refemble the webs of fpi^ers, and
which the Spaniards for that reafon call
arane ; in vegetation, or branches formed
by octahedrons, inferted one in the other.
Some of thefe fpecimens exhibit the mark
of a leaf of fern, others are cubes and fingle
octahedrons, whofe angles are truncated;
the latter are rare. Native filver is often
difperfed in a quartzofe gangue, and is
fometimes met with in fat earths ; it is
found in Peru, in Mexico, and Konfberg in
Norway, at Johan Georgenftadt, and at Eh-
renfriedenfdorf in Saxony, at St. Marie at
Allemont in Dauphiny, &c. This metal is
pot naturally found in the ftate of calx,

2. Native filver united to gpld, copper,
iron, arfenic, regulus of antimony, or to

X 4 gold

328 SILVER.

gold and copper together, or to arfenic and
iron together. Thefe varieties of native
filver alloyed, are found at Freyberg in Sax-
ony, and in the mines of Guadalcanal in
Spain ; but it muft be obferved, that the
foreign fubftances compofe but a fmall pro-
portion.

3. The vitreous filver ore is compofed,
according to moft mineralogifts, of filver
and fulphur; it is of a blackiih grey colour,
refembling lead; fome fpecimens are brown,
greenifh, yellowifh, &c. and it may be cut
with the knife. It is often amorphous,
fometimes cryfiallized in octahedrons, and
in hexahedral prifms, whofe angles are trun-
cated. M. Monnet diftinguifhes a variety,
which iaftead of yielding to the knife like
the others, became reduced into powder.
This ore affords from fixty-two to eighty-
four pounds of filver per quintal. It is
very eafily melted. If it be expofed to a
heat not fufficient to melt it, the fulphur
is diffipated, and virgin filver in vegetation,
or fibres, is obtained.

4. The red filver ore is often of a deep
colour ; fometimes tranfparent, cryfiallized
in cubes, whofe edges are truncated, or in
hexahedral prifms, terminated by tetrahedral
pyramids; at Potofi it is called Roffi-clero.
The filver is combined with fulphur and ar-
fenic; when it is broken, its colour appears
lighter within, and its ftrudture refembles

fmall

SILVER. 329

fmall needles, or convergent prifms, like
ftaladtites. If it be expofed to a fire care-
fully managed, and capable of igniting it,
the iilver is reduced, and forms capillary
vegetations, fimilar to native filver. It af-
fords from fifty-eight to fixty-two pounds
of filver per quintal. The varieties of this
fpecies differ in colour, in form, in weight,
&c. They are in general found in all places
where the other ores of filver are met
with.

5. Silver with arfenic, cobalt, and iron
mineralized by fulphur. Bergman affirms,
that the filver is fometimes fifty hundredths
in this ore. The ore is fometimes grey and
brilliant, often of a dull and tarnifhed co-
lour, with efflorefcences of cobalt. The
goofe dung ore belongs to this fpecies.

6. Grey filver ore, which differs no other-
wife from the copper ore, called falherts,
than in containing a larger proportion of
this precious metal ; it is well cryftallized
in triangular maffes, whofe edges are cut
flopewife. The largeftof thefe cryftals have
fcarcely any brilliancy ; the fmalleft dif-
perfed on a flat gangue, form a very agree-
able "appearance when expofed to the light,
on account of their great brilliancy. The
grey filver ore affords from two to five
marks of filver per quintal. This ore is
fometimes found in organic matters, whofe
form it perfectly imitates 5 it is then called

figurate

330 SILVER.

figurate ore of filver ; fuch is the ore
which refembles the blades of corn, and
that which M. Rome de Lifle obferved in
the form of cones of the pine. Wood
has likewife been found mineralized by this
fpecies of ore. The grey filver ore contains
filver, copper, iron, arfenic, and fulphur ;
when the iron is in fmall proportion, it is
called white filver ore. This laft muft not
be confounded with galena, containing fliv-
ver, which the workmen fometimes call
filver ore.

7. Black filver ore, called nigrillo by the
Spaniards, is nothing more, according to
Lehman and Rome de Lifle, than a decom-
pofition of the red or grey filver ore, or a
fort of middle ftate between thefe ores and
native filver 5 it is often met with. The lat^
ter mineralogift obferves, that the folid,
fpungy, or porous fpecimens, are produced
by the earth and vitreous ore, and are much
richer than thofe fpecimens which are fvi-,
able, and of a pitchy colour, whofe origin
is owing to the alteration of white or grey
filver ores. From thefe caufes it is very fub-
jedl to vary in the quantity of its produdt;
in general it affords from fix or kvcn pounds
to near fixty pounds per quintal.

8. Corneous filver ore, or the natural com-
bination of filver with the muriatic, and a
fmall quantity of vitriolic acid, is of a dirty
yellowifh grey, fometimes it is of a fawa

colour ;

SILVER. 33I

colour; it is rarely tranfparent; eafily yields
to the knife, and melts by the flame of a
candle. It is found cryftallized in cubes,
but moft commonly in irregular mafles.
Portions of native filver are frequently found
inferted in its mafs. It was formerly thought
to contain fulphur and arfenic, but minera-
logifts at prefent are agreed refpedting its
nature. M. Cronftedt, Lehman and Sage,
Woulf, Lommer and Bergman, diftinguifh-
ed the prefence of the marine acid, which
is difengaged by heat. M. Woulf likewife
difcovered, that it contains the vitriolic
acid; it is found in Saxony, at St, Marie,
at Guadalcanal in Spain, and at Allemont
in Dauphiny.

9. The foft filver ore of Wallerius, is na-
tive or mineralized filver, interfperfed in
greater or lefs quantities, in coloured earths.
Many varieties of colour are obfervable in
earths containing filver, from the dirty grey
to the deep brown.

10. Laftly, lilver is found often com-
bined with other metallic matters, in the
ores we have defcribed ; fuch as mifpickel,
the grey cobalt ore, kupfer-nickel, or ore
of nickel, antimony, which often prefents
the variety called plumofe filver ore, blend,
galena, martial pyrites, and white copper
ores : thefe laft are of the fpecies of grey
filver ores. All thefe fubftances frequently
contain a fufficient quantity of filver to be

worked

332 SILVER.

worked with profit; but it is cafy to con*
ceive, that they ought not to be defcribed
like the foregoing, as proper ores of filver,
and that it is fufficient to remark, that they
are partly compofed of this metal.

The affay of filver ores varies according
to their nature ; fuch as contain native filver
ore, require in ftridtnefs nothing more than
feparating and wafhing. Trituration with
running mercury may be ufed for the ac-
curate feparating of this metal from the
marine fubftances, which change it; the
fluid metal diflblves the filver, and may be
afterwards driven off by fire. Sulphureous
filver ores require to be roafted, and after-
wards melted with a greater or lefs quantity
of flux; in this fufion, filver is obtained
commonly alloyed with lead, copper, iron,
&c. For the feparation and accurate afcer-
taining of the quantity of precious metal
contained in this alloy, a procefs entirely
chemical is ufed, which depends on the
properties of the imperfect metals. Lead be-
ing capable of vitrifying, and of carrying
with it, in its vitrification, the imperfedt
metals, fuch as iron and copper, without
acting on filver, this property is ufed to
feparate the perfect metal from thofe with
which it is alloyed ; the filver is melted
with a quantity of lead, which mufl: be fo
much the more confiderable in proportion as
the quantity of bafe metal is fuppofed to be

greater ;

silver. 333

greater. This alloy is then put in flat and
porous veffels, made of calcined bones and
water; this kind of crucible, which is
called a cuppel, is well adapted to abforb
the glafs of lead, which is formed in the
operation of cuppellation. After this pro-
cefs the filver remains pure. In order to de-
termine what quantity of imperfecft metal
it contains, or its degree of finenefs, the
mafs of filver is fuppofed to be divided into
twelve parts, called penny-weights, and
each of thefe penny-weights into twenty-
four grains ; if the mafs of filver has loft
a twelfth of its weight, it is called filver of
eleven penny-weights fine; if it has loft
only a twenty-fourth, it is called filver of
eleven penny-weights, twelve grains fine,
and fo forth. The cuppel, after this opera-
tion, is found to be much heavier, and con-
tains the glafs of lead, and thofe impsrfedl
metals, which were united with ;he iilver,
and have been feparated by the lead. As the
lead itfelf almoft always contains a fmall
quantity of filver, it is necefiary firft to
cuppel it by itfelf, in order to determine the
quantity of the filver it contains, and a
dedu&ion muft be made, from the button of
fine filver obtained, of the fmall portion
known to be contained in the lead made ufe
of, which is called the witnefs. Cuppel-
lation, is attended with a phenomenon by
which the artift is advertifed of the itate of

the

334 SILVER.

the procefs as it goes forward. In proportion
as the filver becomes pure, by the vitrification
and feparation of the lead, it appears much
more brilliant than the portion which is
not yet fine ; the brilliant part increafes by
degrees, and when all the furface of the
metal becomes pure and luminous, the in-
ftant in which it pafTes to this ftate, exhi-
bits a flafh or fulguration, which denotes
that the operation is finished. Cuppelled
filver is very pure with refpect to the im-
perfect metals it may have contained, but it
may contain gold; and as it always contains
a certain quantity, another operation muft
be made to feparate thefe two perfect metals.
As gold is much lefs changeable than filver,
by moil folvents, the filver is difiblved by the
addition of the nitrous or muriatic acids, or
by fulphur; and the gold, on which thefe
folvents have little or no action, remains
pure. TLis method of feparating filver from
gold is called parting; we fhall fpeak of the
different kinds of parting, after having de-
fcribed the action of each of the folvents on
filver, when we mall fpeak of the alloy of
this metal with gold.

The large works where filver is extract-
ed from its ores and purified, are fimilar
to thofe we have defcribed for the aflfay of
the ores of this metal. There are, in general,
three methods of treating filver in the
large way: the firft confifts in triturating

virgin

silver. 335

virgin filver with mercury; this amalgam is
warned to feparate all the earth, the fuper-
fluous mercury is preffed out through the
pores of bags of leather, and the reft is
feparated by diftillation in iron retorts; after
which the filver is melted and caft into
ingots. This procefs cannot be ufed with
filver ores that contain fulphur : thefe are
roafted and mixed with lead, to refine the
precious metal by cuppsllation. Rich filver
ores are treated in this manner, but the
poorer ores are treated in a different manner
from the two foregoing; they are melted
without previous roafting, with a fmall
quantity of pyrites. This fufion, which is
called the crude fufion, affords a mat of
copper in combination of filver, which is
treated with lead in the way of eliquation ;
the latter, which carries down the filver
during the fufion, is afterwards fcorified on
the cupel, and the perfect metal 'remains
pure. Cuppellation in the large way differs
from that which is made in the fmall way;
in this circumftance, viz. that in the firft,
the fcorified lead is driven off by the adfr'on
of a bellows, whereas, in the latter, the glafs
of lead is abforbed by the cuppel.

The filver obtained by the proceffes here
defcribed is, in general, much lefs liable to
alteration than all the metals hitherto
defcribed. The contact of light does not at
all change this metal, however long it be

expofed

336 SILVER.

expofed to it; heat melts it, caufes it to
boil, and to become volatilized, but with-
out alteration. It does not melt in lefs than
a white heat, but is more fufible than copper.
When it has been held in fufion for a certain
time it boils and emits vapour, which con-
fifts of filver volatilized. This fad: is proved
by the exiflence of the metal in the funnels of
chimnies, under which large quantities are
continually melted. It is likewife confirmed
by the capital experiment of the Academi-
cians of Paris, who expofed very pure filver
to the focus of Trudaine's lens. Thefephilo-
fophers obferved, that the melted metal
emitted a thick fume, which completely
filvered a piece of gold held over it.

Silver, when flowly cooled, is papable of
afiuming a regular form, and cryftallizes in
quadrangular pyramids. M. Baume has
obferved that this metal, in cooling, afTumes
a fymmetrical form, which is obfervable on
its furface by fmall fibres, refembling the
feather of a pen. I have obferved that the
fine button obtained by cuppellation often
prefents on its furface fmall fpaces of five
or fix fides arranged among each other,
like a pavement ; but the cryftallization in
tetrahedral pyramids, has not been well ob-
ferved, except by Meffrs. Tillet, and the
Abbe Mongez.

It has been long thought, and fome che-
mifts ftill are of opinion, that filver is in-

deftru&ible

SILVER. 337

deftru&ible by the combined adtion of heat
and air. It is certain that this metal kept in
fufion without contact of air, does not ap-
pear to be fenfibly altered; yet Junker had
affirmed, that by treating it a long time in
the reverberatory furnace, in the manner of
Ifaacus Hollandus, filver was changed into
a vitreous calx. This experiment has been
confirmed by Macquer. That learned chemift
expofed filver twenty fucceffive times in a
porcelain crucible to the fire of the furnace
at Seves, and at the twentieth fuiion he ob-
tained a vitriform matter of an olive green,
which appeared to be a true glafs of filver.
This metal when heated in the focus of the
burning glafs, has always exhibited a white
pulverulent matter on its furface, and a
greenifh vitreous covering on the fupport it
refted upon. Thefe two facts remove all
doubt refpecting the alteration of filver 5
though it is much more difficult to calcine
than other metallic matters, yet it is capable
of being converted after a length of time
into a white calx, which treated in a violent
fire, affords an olive-coloured glafs. It
may perhaps be poffible to obtain a calx of
filver, by heating this metal when reduced
into very fine laminae, or in leaves, for a very
long time in a matrafs, as is done with mer-
cury. At all events it is certain, that
filver does not combine with the bafe
of vital air without great difficulty, and
Vol. III. Y that

338 SILVER.

that heat does not favour this combination
in the fame manner as it does with almoft
all the other metals ; but on the contrary,
difengages that principle from it very rea-
dily : for the calces of filver are all eafily
reduced without addition, a circumftance
which depends on the flight adherence of
the oxyginous principle, which by heat is
difengaged in the form of vital air.

Silver is not changed by the adlion of air,
its furface being fcarcely tarnifhed by a very
long expofure to that fluid. Water does not
adt on it. Earths do not combine with it,
but it is probable that its calx would give
an olive green colour to glaffes with which
it might be fufed.

The falino-terreftrial matters and the
alkalies, do not fenfibly a<ft on filver. Vi-
triolic acid diflblves it when very concen-
trated or boiling, and the metal is greatly
divided. Much fulphureous gas is difen-
gaged during this folution; the filver is
converted into a white matter, on which
fpirit of vitriol muft be poured, in order
to hold it in folution : very fmall needles
of lunar vitriol are obtained by evaporating
this liquor. I have feveral times obtained
vitriol of iilver in plates, formed by the
union of thefe needles length-wife. This
fait melts in the fire, and is very fixed; it is
decompofabie by alkalies, iron, copper, zink,
mercury, &c. All the precipitates obtained

by

silver. 339

by alkalies, are reducible without addition,
and become converted into fine filver, in
clofed veflels.

The nitrous acid diflblves filver with rapi-
dity, and even without the afiiftance of
heat. This folution is fometimes performed
fo quickly, that in order to prevent the in-
convenience that might arife, it is neceffary
to ufe filver in a lump. A large quantity of
nitrous gas is difengaged, and a white pre-
cipitate, more or lefs abundant, is formed,
if the fpirit of nitre contained a portion of
vitriolic or muriatic acid. The fpirit of
nitre ufually becomes of a blue or green
colour, but lofes this colour, and becomes
tranfparent as foon as the folution is finifh-
ed, if the filver made ufe of be pure; but
on the contrary, a greenifh tinge remains
when the filver contains copper. The pureft
filver which can be employed, fometimes
contains gold : in this cafe, as the nitrous
acid has fcarcely any a&icn on this perfect
metal, this laft is feparated in the form of
blackifh flocks, in proportion as the filver is
diflblved. From the difference of the adtion
of this acid on thefe two metals, it is fuccefs-
fully employed in feparating them from each
other, in the operation of parting by aqua-
fortis. The nitrous acid diffolves more than
half its weight of filver : this folution is
exceedingly cauftic, tinges the epidermis of
a black colour, and intirely corrodes it.
Y 2 When

340 SILVER,

When highly charged with the metal, it de-
pofits flender brilliant cryftals, refembling
thofe of fedative fait; when the one half is
evaporated, it affords, by cooling, flat cryftals,
which are either hexagonal, or triangular, or
fquare, and appear to be formed of a great
number of fmall needles, placed one befide
the other. Thefe plates are placed obliquely
on each others they are transparent, and very
cauftic, and are called nitre of filver, lunar
nitre, or lunar cryftals. Lunar nitre is quickly
altered by the contadl of light, and blackened
by combuftible vapours. It detonates on
heated charcoal, and leaves a white powder,
which is pure filver. It is very fufible: if it
be expofed to heat in a crucible, it firft fwells
up and lofes the water of cryftallization, after
which it remains in fufion ; and if fuffered
to cool in this ftate, it appears to be a grey
mafs, and forms a preparation known in
pharmacy and furgery, by the name of lapis
infernalis. It is not neceffary in making
this preparation, to ufe the cryftals of lunar
nitre, which are difficult and expenfive to
obtain $ as it is fufficient to evaporate a fo-
lution of filver in the nitrous acid to dry-
nefs, and to put this refidue in a crucible or
filver ladle, as M. Baume advifes, and to
heat it flowly till it is in an undifturbed fufion,
in which flate it muft be poured into a mould,
to give it the form of fmall cylinders. If the
cylinders of lapis infernalis be broken, they
• are

SILVER. 34I

arc found to be of a needle-formed texture,
radiating from the axis of each cylinder.
Lunar nitre muft not be too long heated to
make the lapis infernalis, as by that means
a part of the fait would be decompofed, and
a button of iilver would be found at the
bottom of the crucible. To afcertain what
pafles in this operation, I have diitilled lunar
cryftals in the pneumato-chemical appara-
tus : they afforded nitrous gas, and a large
quantity of very pure vital air ; the filver
was recovered in the matrafs, intirely re-
duced. The glafs was opake like enamel,
and of a beautiful marron brown colour.
The brown colour of the glafs in this ex-
periment, doubtlefs arifes from manganefe,
or fome other fubftance contained in it ; for
the colour of glafs formed by the calx of
filver, is of an olive green, as we have already
obferved.

Lunar nitre expofed to the air, does not
attract moiflure ; it is very foluble in wa-
ter, and may be cryftallized by the flow
evaporation of that fluid.

The nitrous folution of filver is decom-
pofed by the falino-terreftrial fubflances and
by alkalies, but with very different pheno-
mena, according to the ftate of the fub-
flances. Lime-water forms a very abundant
olive-coloured precipitate; cretaceous fixed
alkalies precipitate it of a white colour; the
cauftic volatile alkali of a green, inclining

Y 3 to

342 SILVER.

to olive: the latter precipitation takes place
after a confiderable time.

Though the nitrous acid adls with more
energy than any other on filver, it has not
the ftrongeft adhefion and affinity with that
metal. The vitriolic and muriatic acids are
capable of depriving it of the calx of filver
which it may hold in folution. Hence it is,
that a few drops of thefe acids poured into a
nitrous folution of filver, produce a precipi-
tate of a white powder when the vitriolic
acid is ufed, or a thick coagulum when the
muriatic acid is ufed. In the firft cafe vi-
triol of filver is formed ; in the fecond, mu-
riate of fiiver. Thefe two falts not being
very foluble, are precipitated. It is not ne-
ceffary to ufe the vitriolic and muriatic acids
in a difengaged ftate, to produce thefe decom-
pofitions ; the neutral falts refulting from
their union with alkalies and earthy matters,
may be employed with equal advantage. A
double decompofition or combination then
takes place, becaufe the nitrous acid being
feparated from the filver, unites with the
bafe of the vitriolic and muriatic fait. This
difference of affinity between the acids and
filver, is the bafis of a procefs ufed for pro-
curing the nitrous acid in a ftate of purity,
without any mixture of other acids ; fuch
in a word as is neceffary for many operations
in metallurgy, and for the moft part of che-
mical refearches. As it feldom happens in

the

silver. 343

the diftillation of fpirit of nitre, that this
fluid is not mixed with a certain quantity of
vitriolic and muriatic acid, chemifts have
endeavoured to difcover methods of fepa-
rating thefe feveral fluids, and they avail
themfelves with fuccefs of the nitrous folu-
tion of filver for this purpofe. The lunar
folution is poured into the impure nitrous
acid, till no more precipitate is formed.
The depofition formed by the vitriol of fil-
ver, or lunar cornea, is fuffered to fubfide;
the acid is decanted and diftilled by a gentle
heat, to feparate it from the fmall portion of
lunar fait it may contain; and the product is
very pure nitrous acid, called precipitated
nitrous acid.

Moft metallic matters are capable of de-
compofing the nitrous folution of filver, be-
caufe they have a ftronger affinity than that
metal with the nitrous acid. The neutral ar-
fenical fait difiblved in water, produces a
reddifh precipitate in the nitrous folution,
which confifts of filver united with arfenic ;
this precipitate refembles the red ore of fil-
ver. Silver may be precipitated in its metallic
ftate by moft metals and femi-metals -y but
we fhall more particularly attend to the fe-
paration of this perfect metal by mercury
or by copper, becaufe of the phenomena the
firft prefents, and the utility of the latter.

Silver feparated from the nitrous acid by
mercury, is in its metallic ftate, and the

Y 4 flownefs

344 SILVER,

flownefs of its precipitation produces a pe*
culiar fymetrical amalgam, known by the
name of Arbor Dianas, or the philofophical
tree. There are many procefTes for obtain-
ing^this cryftallization. Lemery directs one
ounce of fine filver to be diffolved in ni-
trous acid of moderate ftrength : this folu-
tion is to be diluted with about twenty
ounces of diftilled water, and two ounces of
mercury are to be added : in forty days a
very beautiful vegetation is formed. Horn-
berg has prefcribed a much fhorter procefs :
according to this chemift, an amalgam of
four drams of leaf filver, with two drams
of mercury, muft be made in the cold. This
amalgam is to be diffolved in a futficient
quantity of nitrous acid, and a pound and
a half of diftilled water muft be added to
the folution. A little ball of the foft amal-
gam of filver muft be put into an ounce of
this liquid, and the precipitation takes place
almoft inftantly. The precipitated filver,
united to a portion of the mercury, dif-
pofes itfelf in fibres of a prifmatic appear-
ance on the fufface of the amalgam : other
fibres appear, and infert themfelves in the
foregoing, fo as to exhibit a vegetation in
the fofm of a bum. Laftly, M. Baume
has defcribed a method of obtaining the
Arbor Dianae, which differs in fome refpects
from that of Horn berg, and fucceeds with
greater certainty; hedire&s fi^ drachms of the

felution

silver. 345

folution of Giver, and four of the folution
of mercury, in the nitrous acid, both well
faturated, to be mixed, and five ounces of
diftilled water to be added to this liquor.
The mixture muft be poured into an earthen
veffel, upon fix drachms of an amalgam of
filver, made with feven parts of mercury, and
one part of iilver. Thefe two methods fuc-
ceed much more quickly than that of Le^
mery, by the reciprocal aCtion and affinity
between the metallic fubftances. In fadt,
the mercury contained in the folution, at-
tracts that of the amalgam ; the filver con-
tained in the latter aCts likewife on that
which is held in folution, and from thefe
attractions, a quicker precipitation of the
filver takes place. The mercury which com-
pofes a part of the amalgam, being more
abundant than is neceflary to precipitate the
filver from the folution, produces likewife a
third eftedt of confiderable importance ; it
attracts the filver by the affinity and tenden-
cy it has to combine with that metal, and it
-effectually combines with it; fince the vege-
tation of the Arbor Dianas are a true brittle
amalgam of a cryftallized form. This cry-
ilallization fucceeds much better in conical
veffels, or glaffes, than in round or open vef-
fels, fuch as the cucurbit recommended by
M. Baume. It may likewife be obkrved,
that it is neceffary to place the vtflel in
which the experiment is made, in a fituation

where

346 SILVER.

where it may not be fhaken, or agitated, as
fuch circumftances would effectually prevent
the fymetrical arrangement of the amalgam.

Copper plunged in the folution of filver,
precipitates this metal likewife in a brilliant
and metallic form. This pfocefs is ufually
employed to feparate the filver from its fol-
vent, after the procefs of parting. Plates of
copper are immerfed in the folution, or the
folution itfelf is poured into a veffel of cop-
per; the filver immediately becomes feparate
ed in whitifh grey flocks. When the liquor
becomes blue, and is deprived of all its filver,
it is decanted off; the filver, after being wafhed
feveral times in water, is melted in a crucible,
and cupelled, in order to feparate it from the
portion of copper with which it united dur^-
ing the feparation, The filver afforded by
this operation, is the pureft of all ; it is
twelve penny- weights fine. From thefe two
precipitations of filver by mercury and cop-
per, we fee, that metals Separated from their
folvents by other metallic matters, are preci-
pitated with all their properties. This pheno-
menon depends, as we have obferved in the
hiftory of copper, on the circumflance that
the metals, immerfed in the folution of
filver, take the oxyginous principle from the
latter, by virtue of their ftronger affinity.

The muriatic acid does not immediately
diffolve filver, but it perfectly difiblves its
calces. When this acid is furcharged with

the

SILVER. 347

the oxyginous principle, and in the dephlo-
gifticated ftate, it readily diflblves that metal.
This no doubt accounts for what happens in
the procefs of dry parting. The operation
confifts in expofing plates of gold alloyed
with filver to heat in a cement, compofed of
a mixture of martial vitriol and common
fait : the vitriolic acid difengages the mu-
riatic acid, gives it a portion of its oxyginous
principle, and the latter adts on, and diflblves
the filver.

A much fhorter and eafier procefs is ufed
to combine the muriatic acid with the calx
of filver, by pouring it into a nitrous folu-
tion of the metal. The very abundant
precipitate, which is inftantly formed, is a
combination of the muriatic acid with filver,
which has a ftronger affinity with this acid
than with that of nitre, and confequently
quits the latter to unite with the former.
The fame combination is obtained by pour-
ing the muriatic acid into a folution of vitriol
of filver, becaufe this has a ftronger affinity
than the vitriolic acid with the metal. The
muriatic acid may likewife be combined with
filver, by heating it on a calx of the metal
precipitated from the nitrous acid by fixed
alkali.

The muriate of filver poffefles many pro-
perties which deferve to be known; it is fo
fufible, that it melts when expofed in an
apothecary's phial to a mild heat ; as for

example,

348 SILVER.

example, that of hot afhes. By this fufion
it is converted into a grey and femi-tranfpa-
rent fubftance, refembling horn, and for that
reafon has been called luna cornea. If it be
poured on a ftone, it becomes fixed in the
form of a friable matter, cryftallizedasitwere
in fine filvery needles. When heated for a
long time with contact of air, it is decom-
pofed; it pafles ealily through the crucibles;
part is volatilized, and part is reduced into
metal, affording globules of filver,interfperfed
among the portion of the luna cornea, which
is not yet decompofed. Luna cornea expofed
to light, lofes its white colour, and becomes
brown in a fhort time. It diffolves in water,
in but a very fmall quantity; a pound of
diftilled boiling water taking up only three
or four grains, according to the experiment
of M. Monnet. Alkalies are capable of de^
compofing luna cornea diffolved in water,
or in the dry way by heat ; this method
affords the pureft and fineft filver known. A
mixture of four parts of vegetable alkali, or
chalk of pot-afh, with one part of luna cor-
nea, is melted in a crucible : when it is in
flrong fufion, it is taken from the fire, fuf-
fered to cool, and broken ; the filver is
found beneath the muriate of pot-afh form-
ed in the operation, and the fuper-abundant
portion of alkali employed. M. Baume,
the inventor of this procefs, affirms, that
the quantity of alkali he diredts, prevents

the

silver. 349

the luna cornea from paffing through the
crucible, by acting on all its parts, which it
decompofes at once. Margraaf has given
another procefs for reducing luna cornea,
and obtaining perfectly pure filver : five
drachms fixteen grains of luna cornea are
triturated in a mortar, with one ounce and
a half of concrete volatile alkali, or ammo-
niacal chalk, a fufficient quantity of diftilled
water being added to form a parte ; this mix-
ture is agitated till the fwelling and effer-
vefcence, which are excited, have fubfided.
Three ounces of purified mercury are then
added, and triturated, till a perfect amalgam
of filver is obtained : this is warned with a
large quantity of water, the trituration ftill
being continued, and the warning renewed,
till the water partes off very clear, and the
amalgam is very bright. The amalgam being
then dried and diftilled in a retort, till the
veflel has acquired a white heat ; the mercury
partes into the receiver, and the filver is
found pure at the bottom of the retort. In
this way the metal is obtained in the mofl
perfedl ftate of purity, and without anyfen-
fible lofs. This is the filver which ought
to be ufed in the nicer chemical experi-
ments. The water employed in warning
the mixture carries off two fubftances; a
certain quantity of fal-ammoniac, which it
holds in folution, and a white infoluble pow-
der. When the latter is fublimed, a fmall

quantity

350 SILVER.

quantity of filver is found at the bottom of
the fublimatory veffel. This experiment
fhews, that luna cornea is not completely de-
compofed, unlefs by the double affinity. In
fact, in the procefs of Margraaf, the volatile
alkali does not unite with the muriatic
acid, but becaufe the filver combines on its
part with the mercury, which attracts and
tends to feparate it from the acid, which
the alkali alone could not do. It is eafily
feen, that this long and expenfive operation
can only be ufed in the fmall works of a
chemical laboratory. If luna cornea in large
quantities be required to be reduced, either
fixed alkalies, or fome metallic fubftance,
mufl be ufed, which have a ftronger affinity
than filver with the marine acid ; fuch,
among others, are the regulus of antimony,
lead, tin, iron, &c. If one part of luna cor-
nea be melted in a crucible with three parts
of one of thefe metals, the filver will be
found reduced at the bottom of the crucible,
and the metal united to the muriatic acid.
Silver precipitated in this manner, is very
impure, and always contains a portion of
the metal ufed for the reduction ; and as
lead is moft commonly employed, according
to the advice of KunkeJ, the filver obtained
requires to be cupelled ; it cannot confe-
quently be brought to the fame ftate of purity
with the filver reduced directly by alka-
lies, or by the procefs of Margraaf.

Aqua

SILVER. 351

Aqua regia ads ftrongly on filver, and
precipitates it in proportion as it is difTolved :
this effect may eafily be underftood; the ni-
trous acid firft diffblves the metal, and the
muriatic acid feizes it, forming luna cornea,
which falls down on account of its fmall
degree of folubility. This procefs may be
ufed to feparate filver contained in gold.

"The action of the other acids on filver
are not well known ; it is only known that
a folution of borax produces a very abun-
dant white precipitate from the nitrous fo-
lution of this metal, and that this precipi-
tate confifts of the fedative acid united to a
portion of the calx of filver.

This metal does not appear to be altered
by neutral falts ; it is certain that it does
not detonate with nitre, nor decompofe fal-
ammoniac. This unchangeablenefs of filver
with nitre, affords a good method of fepa-
rating it from the imperfect metals with
which it may be united, fuch as copper,
lead, &c. The alloyed metal muft be melt-
ed with the addition of nitre; the fait deto-
nates and burns the portion of foreign im-
perfect metal, and the filver remains at the
bottom of the crucible, in a ftate of much
greater purity than before.

Almoft all combuftible matters have a cer-
tain action on filver; no metal is more
quickly tarniflied and coloured by inflam-
mable matters; hepatic gas, from whatever

fubfiance

35^ SILVER*

fubftance it may be difengaged, communi-
cates to it immediately upon contact, a blue or
violet colour, inclining to black, and great*
ly diminishes its du&ility. It is well known
that hepatic animal vapours, fuch as thofe
of neceflary houfes, putrefied urine, and hot
eggs, produce the fame effect on this metal.
The mutual adlion of thefe two bodies, and
the kind of combination which arifes from
them, has not yet been examined into.

Sulphur combines readily with filver ; this
combination is ufually made by Gratifying
plates of the metal with flowers of fulphur
in the crucible^ and quickly fufing the mix-
ture : a deep violet coloured mafs is produced,
much more foluble than filver, brittle, and
difpofedin needles; in a word, a true artificial
ore. This combination is eafily decompo-
fed by the aftion of fire, becaufe of the vo-
latility of the fulphur and the fixity of fil-
ver ; the fulphur is confumed and difiipated,
and the filver remains pure; liver of ful-
phur diffolves this metal in the dry way.
When one part of filver is melted with
three parts of liver of fulphur, the metal
difappears, and becomes foluble in water,
together with the hepar. If an acid be
poured into this folution, a black fulphure-
ous precipitate of filver is obtained. Silver
left in liquid liver of fulphur, quickly af-
fumes a black colour, and the fulphur ap-
pears to quit the alkali to unite with, and

mineralize

silver. 353

mineralize the metal, as we have likewife
obierved it does with mercury.

Silver unites with arfenic, which renders
it brittle ; but the action of the arfenical acid
on this perfect metal, is not yet known.

It does not combine with cobalt without
difficulty.

It unites perfectly eafily with bifrriuth, and
forms a brittle mixed metal, whofe ipecific
gravity is greater than that of the two me-
tals feparately taken. According to Cron-
ftedt, filver does not unite with nickel ;
but when thefe metals are melted together,
they remain befide each other, as if their
fpecific gravity were precifely the fame.

It mixes by fufion with regulus of anti-
mony, and affords a very brittle alloy. It
feems capable of decompofing antimony,
and of uniting with the fulphur of that
mineral, with which it has a ftronger af-
finity than the regulus of the antimony.

Silver combines readily with zink by fu-
fion ; alloy is produced by this combina-
tion, granulated at its furface, and \ery
brittle.

It difiblves completely, and even without
heat, in mercury. To produce this folution,
filver leaf may be triturated with the metal-
lic fluid ; an amalgam is immediately pro-
duced, whofe confidence varies according to
the relative quantities of the two fubftances.
This amalgam is capable of affuming a re-
Vol. III. Z gular

354 SILVER.

gular form y by fufion and flow cooling, it
affords tetrahedral prifmatic cryftals, termi-
nated by pyramids of the fame form. The
mercury affumes a degree of fixity in this
combination ; for a much ftronger heat is
neceffary to feparate it from the filver, than
would be required to volatilize it alone.
Silver is capable of decompofing corrofive
fublimate either by the dry or the humid
way.

It unites perfectly with tin, but lofes its
ductility by the fmalleft addition of this
metal.

It readily becomes alloyed with lead,
which renders it very fufible, and deprives
it of its elailicity and fonorous quality.

It unites with iron, and forms an alloy,
which has been but little examined into, but
may probably become of the greateft utility
in the arts.

Laftly, it melts and combines in all pro-
portions with copper ; the latter does not
deprive it of its dudlility, but renders it
harder and more fonorous, forming an alloy
which is often employed in the arts.

Silver is a metal highly ufeful, on ac-
count of its ductility, and its indeftruclibi-
lity by fire and by air. Its brilliancy renders
it capable of ferving the purpoies of orna-
ment. It is applied on the furface of dif-
ferent bodies, and even on copper; and like-
wife enters into the texture of rich iilks ;
but its moil confiderable ufe is that of afford-
ing

gold. 355

ing a matter, proper by its hardnefs and
ductility, to form vefTels of all forts. Silver
plate is ufually alloyed with one twenty-
fourth of copper, which gives it a greater
degree of hardnefs and coherence, and does
not render it at all noxious, becaufe the
twenty-three parts of filver cover the cop-
per, and intirely prevent its noxious effects.
Laftly, filver is employed as a medium of
exchange, in the form of money ; in this
cafe it is alloyed with one twelfth part of
copper, and is confequently eleven penny-
weights fine.

CHAP. XX.

Concerning Gold.

GOLD, or fol of the alchemifts, is the
moft perfect and the lead: changeable
metal known ; it is of a yellow brilliant
colour : no other fubftance in nature is fo
heavy, for it lofes only between one nineteenth
and one twentieth of its weight in water.*
Neither its hardnefs nor its elafticity are
very confiderable. Its aftonifhing ductility,
which are well afcertained by the fmallnefs
of gold wire, and the thinnefs of gold leaf,
is fuch, that an ounce of this metal is fufli-

Z 2 cient

* Platina is much heavier. See the note at the end of that
article. T.

3^6 GOLD.

cient to gild a filver wire of 444 leagues in
length, and it is reduced into plates fuffi-
ciently thin to be blown away by the wind.
A grain of gold, according to the calculation
of Lewis, is capable of covering the furface
of more than 1400 fquare inches. It is the
moft tenacious of all the metals. A gold
wire of one tenth of an inch in diameter,
being capable of fuftaining a weight of 500
pounds without breaking. Gold foon be-
comes hard under the hammer, but imme-
diately recovers its ductility by ignition.

The colour of gold is fufceptible of con-
fiderable variety; it is more or lefs yellow,
and fome fpecimens are almoft white ; thefe
differences however feem to depend on fome
alloy. Gold has neither fmell nor tafte ; it
is capable of cryftallizing by cooling, in fhort
quadrangular pyramids, as Meflrs. Tillet
and Mongez have obferved.

Gold is almoft always found in a native or
virgin ftate : it is fometimes met with in
fmall infulated maffes, difpofed on a matrix
of quartz ; fometimes it is in fmall fpangles,
intermixed with fand at the bottom of
waters; and laftly, it is obtained from many
ores into the compofition of which it enters,
fuch as galena, blend, red filver ore, and vir-
gin filver. It is almoft always united with
a certain quantity of filver and other metals,
forming natural alloys.

There

gold. 357

There are many varieties of native gold,-
in plates, in grains, in oftahedral cryftals, in
four fided prifms, ftriated in filaments, and
in irregular maffes. Mr. Sage thinks, that
native gold in prifms is united to a certain
quantity of mercury, which renders it
brittle.

. Modern mineralogists admit feveral fpecies
of gold ores.

i. Native gold united to filver, copper,
iron, &c. found in Peru, Mexico, Hungary,
Tranfylvania, &c.

2. The auriferous pyrites : it is not eafily
diftinguifhed by the eye from other pyrites;
the gold is feparated by treating the ore with
the nitrous acid, and waihing the refidue. The
gold feems to be merely mixed with martial
pyrites. Certain arfenical pyrites, and in par-
ticular thofe of Salfberg, in Tyrol, likewife
contain a fmall portion of gold.

3. Gold mixed with filver, lead, or iron,
mineralized by fulphur. This auriferous
ore is of a very compounded nature accord-
ing to Mr. Sage; it confifts of blend, galena,
fpecular antimony, copper, filver, and iron ;
the gold melts and iffues out with the lead
when the mafs is expofed to heat ; it comes
from Nagaya in Tranfylvania.

The method of affaying ores of gold, dif-
fers according to the nature of the mineral ;
pulverizing and wafhing are furficient for the
feparating of native gold from its matrix;

Z 3 if

358 GOLD..

if the gold be alloyed with other metals, it
will be neceffary to roaft the ore, and the
metal, after being extracted by fufion, mud
be cupelled with lead, and parted with aqua
fortis.

The method of extra<fting gold from its
ores may be eafily underflood, from the
confideration of the metallurgic procefTes we
have already defcribed. Native gold re-
quires only to be feparated from its gangue •
for this purpofe it is ground, and afterwards
wafhed; it is then triturated in a mortar, fil-
led with water, together with ten or twelve
parts of mercury : the water which wafhes
the metallic fubftance, and feparates thofe
parts which are merely earthy, muft be de^
canted off. When the amalgam formed in this
operation is thus deprived of all its earth,
and appears very pure, it is preffed in bags
of fhamoy leather ; a great part of the mer-
cury pafies through the pores of the fkin,
and the gold remains united with a certain
portion of the femi-metal. The remaining
mercury is feparated by diftillation from the
amalgam, and the pure gold being fufed, is
caft into bars or ingots. The gold which
is found combined in the ores of other me^
tals, fuch as thofe of lead and copper, is
extradted by cupellation and parting from
the former of thefe metals ; and from the
latter it is obtained by eliquation with lead,

which

GOLD. 2S9

which carries off the filver and gold. Cu-
pellation afterwards feparates the lead, and
the procefs of parting feparates the filver, as
we fhall hereafter obferve.

Gold expofed to the fire becomes red long
before it melts. In a ftrong heat it appears
of a brilliant fea green colour; but it does not
melt till heated to whitenefs, and cryftalli-
zes by flow cooling. The ftrongefl: heat of
a furnace continued for an indefinite time,
does not produce any change in this me-
tal : Kunckel and Boyle made this experi-
ment, by expofing gold for feveral months
to the fire of a glafs-houfe. This inalterabi-
lity however is merely relative to the fires
we are able to make with combuftible fub-
ftances ; for it appears certain that aftronger
heat, fuch as that of the fun concentrated
by glafs lenfes, is capable of depriving it of
its metallic properties. Homberg obferved
that this metal, when expofed to the focus of
the lens of Tfchirnhaufen, fumed, was vola-
tilized, and even vitrified. Macquer found,
that gold expofed to the focus of the lens of
M. Trudaine, melted and exhaled a fume
which gilded filver, and was therefore gold
in a volatile ftate j that the globule of melt-
ed gold was agitated with a rapid circular
motion, and became coloured with a dull,
and as it were, calciform pellicle ; and laft-
ly, that a violet vitrification was formed on
Z 4 the

j60 GOLD.

the middle of the globule. This vitrifica-
tion gradually extended, and produced a kind
of button, flatter or of a larger curvature
than that of the globule, which ftuck on
the globule itfelf, as the tranfparent cornea
appears on the fclerotica of the eye. This
glafs increafed in fize, while the gold itfelf
continually diminished ; the fupport always
appeared tinged with a purple colour, appa-
rently produced by the abforption of part
of the glafs.

Time did not permit Macquer to vitrify
intirely a certain quantity of gold. This cele-
brated chemift obferves, that it is a neceflary
condition, that the violet glafs /hould be
reduced with combuftible matters, in order
to juftify the aflertion, that it is the calx of
that perfect metal, which would evidently
appear to be the cafe, if it became revived
into gold. However this may be, we think
it may be confidered as a true vitrified calx
of gold, with fo much the greater probabi-
lity, as in many operations with this metal,
prefently to be defcribed, the purple co-
lour is conftantly produced, and that many
preparations of gold are employed to give
that colour to enamel and porcelain. Gold
is therefore calcinable like the other metals,
and only requires, as likewife does filver, a
flronger heat, and a longer time to unite
with the bafe of air than other metallic fub-
ftances. Thefe circumftances, no doubt,

bear

gold. 36r

bear relation to its denfity, and its fmall
tendency to unite with the oxyginous prin-
ciple. Gold may be perfectly calcined by
the action of a ftrong ele&ric fpark.

Gold is not changed by expofure to air;
its furface becomes tarnifhed merely by the
depofition of foreign bodies which continu-
ally float in the atmofphere. Water does
not at all change it, though, according to
the experiments of Lagaraye, it feems capa-
ble of dividing it nearly in the fame manner
as it does iron.

Gold does not combine with earths, or
the falino-terreftrial fubftances in its metal-
lic ftate ; its calx makes a part of the compo-
iition of glaffes, to which it gives a violet
or purple colour.

Gold is not at all altered by the mod
concentrated vitriolic acid, even though
heated.

The nitrous acid appears capable of dif-
folving a fmall portion of this metal, per-
haps rather mechanically, than by a true
combination. Brandt was one of the firft
chemifts who affirmed, that the nitrous acid
diflblves gold, and his ailertion has been
confirmed by Scheffer and Bergman ; but it
muft be obferved, that experiments made by
the whole clafs of chemifts of the academy
of Paris, fhew, that the nitrous acid only
takes up a fmall portion of gold in peculiar

circumftances,

362 GOLD.

circumftances, not mentioned by thofe che-
mifts. Deyeux, member of the College of
Pharmacy, has obferved, that the nitrous
acid diflblves gold only when it is fmok-
ing, and charged with nitrous gas ; he thinks
that the acid in this ftate is not pure, and
affirms that it is loaded with gas, and by
that means converted into a kind of aqua
regia.

The muriatic acid alone, and in a ftate
of purity, does not fenfibly adt on gold.
MefTrs. Scheele and Bergman have difcover-
ed, that this acid, when dephlogifticated or
aerated, diflblves gold abfolutely in the fame
manner as aqua regia, and forms with this
metal the fame fait which is ufually obtain-
ed with the mixed acid or aqua regia. The
folution appears to take place in confequence
of the excefs of oxyginous principle united
to the muriatic acid; it is made without
feniible effervefcence, a circumftance com-
mon to all metallic folutions in the aerated
muriatic acid.

Aqua regia has been confidered as the
true folvent of gold ; it does not however
diflblve it better than the aerated muriatic
acid. Without repeating in this place, what
we have elfewhere laid refpecting the na-
ture, properties, and differences of this mix-
ed acid, according to the quantity of the
two acids combined together in its forma-
tion, we fhall only attend to its action on

gold.

GOLD, 363

gold. As foon as the aqua regia comes in
conta<ft with the metal, it attacks it with,
an effervefcence which is fo much the
ftronger, as the acid is more concentrated,
the temperature higher, and the gold more
minutely divided. The operation may be
haftened by a gentle heat, or at lead its
commencement may be forwarded; the
bubbles fucceed each other without inter-
miffion, till a portion of the metal is dif-
folved, after which this appearance gradually
ceafes, and cannot be renewed but by agita-
tion or heat ; nitrous gas is diiengaged dur-
ing this folution. The aqua regia, when fa-
turated with as much gold as it is capable of
taking up, is of a yellow colour, more or
lefs deep, coniiderably cauflic, corrodes
animal matters, and tinges them of a deep
purple colour. By cautious evaporation it
affords cryflals of a beautiful gold colour,
refembling topazes, and appearing to coniift
of truncated odlahedrons, and fometimes te-
trahedral prifms. This crystallization is
not eafily effe&ed. M. Monn-t thinks that
it arifes from the neutral fait formed in the
aqua regia, and affirms that it is neceffary,
in order to obtain thefe cryftals, that an aqua
regia made with nitrous acid and fal-arnmo-
niac, or marine fait, mould be employed:
the mixed acid then contains either nitre of
foda, or ammoniacal nitre. According to
this chemift, either of thefe neutral fairs

caufes

364 GOLD.

caufes the crystallization of gold : never-
thelefs it appears, that a folution of gold, in
an aqua regia made with the pure muriatic
and nitrous acid, is capable of affording cry-
ftals ; and Bergman confiders this fait as a
true muriate of gold : if the cryftals be
heated, they melt and affume a red colour.
This fait ftrongly attracts the moifture of
the air. When a folution of gold is dif-
tilled, a beautiful red liquor is obtained,
which is found to confift of the muriatic
acid, charged with a fmall portion of gold.
The alchemifts, whofe labours with gold
were very great, gave the name of the
red lion to this liquor. Some cryftals of
gold of a reddifh yellow colour, are likewife
iublimed in this procefs ; but the greateft
part of the metal remains at the bottom of
the retort, and requires only to be fufed, in
order to regain all its properties.

The folution of gold is decompofed by a
great number of intermediums. Lime and
magnefia precipitate gold in the form of a
yellowifh powder ; fixed alkalies exhibit the
fame phenomenon -, but it mud be obferv-
ed, that the precipitate is afforded very flow-
ly, and that the folution affumes a reddifh
colour, if more alkali be added than is ne-
ceffary; becaufe the excefs of this fait re-
diffolves the precipitated gold. The pre-
cipitate of gold may be reduced by heat
alone, in cloied veifels, this calx readily fuf-

fering

GOLD. 365

fering the oxyginous principle to become
difengaged in the form of vital air. It is
neverthelefs capable of being fufed with vitre-
ous matters, and communicating a purple
colour to them ; for the precipitate of gold
formed by the mixture of a folution of
gold, and the liquor of flints is ufed in
enamels and porcelain.

Gold precipitated by fixed alkalies, has
likewife a property very different from that
of gold in its metallic ftate ; it is foluble in
the pure vitriolic nitrous and muriatic acids ;
all thefe acids heated on the yellowifh pre-
cipitate of gold, readily diffolve it, but do
not become fufriciently faturated to afford
cryftals. When the folutions are evapo-
rated, the gold is readily precipitated, as
likewife happens by mere reft. M. Mon-
net has obferved, concerning the precipita-
tion of the folution of gold by nut-galls,* a

faft

* As we have only fpoken of the precipitation of iron by
nut-galls, it will be proper in this place to give a /hort ac-
count of the phenomena this aftringent fubftance prefents
with moft other metallic folutions.

Nut-gall precipitates the folution of cobalt of a light
blue colour; that of zinlc of a cinereous green; of copper,
green which becomes grey and reddifh ; of filver, firft
reddifh ftriae, which foon takes thtf colour of burnt coffee ;
that of gold purple. Thefe facts have been obferved
and defcribed by M. Monnet, who likewife found that the
precipitates are foluble in acids, and that alkalies unite to
the laft-mentioned folutions, without occafioning anv pre-
cipitate.

To

366 GOLD.

fad: which ought not to be overlooked, viz.
that the reddifh precipitate it affords, is
readily foluble irt the nitrous acid, to which
it gives a beautiful blue colour.

Volatile alkali precipitates the folution of
gold in much greater abundance. This pre-
cipitate, which is of a brown yellow, and
fometimes of an orange colour, has the pro-
perty of detonating with a confiderable
noife when gently heated : it is called ful-
minating gold. The volatile alkali is abfo-
lutely neceffary in the production of fulmi-
nating gold ; this preparation may be formed
either by precipitating a folution of gold in
an aqua regia, made with fal-ammoniac, by
the addition of fixed alkali, or by precipi-
tating a folution of gold, made with aqua
regia, cornpofed of pure nitrous and muria-
tic acid : by the addition of volatile alkali
the fulminating gold always weighs one
fourth more than the gold diffolved in aqua
regia. The terrible effects of fulminating
gold, render it neceffary to act with great

To thefe the academicians of Dijon have added the fol-
lowing fa6te : folution of arfenic is not altered by nut-gall ;
that of bifmuth, affords a greenifh precipitate > of nickel, a
white precipitate ; of antimony, a blackifh grey j of lead, a
flate coloured precipitate, whofe furface is covered with a
mixture of green a*id red pellicles ; laftly, that of tin be-
comes of a dirty grey by the mixture of nut-gall, and affords
an abundant precipitate, of a mucilaginous appearance.

Note of the Author.

caution

GOLD. 367

caution in the management of this fub-
ftance : it muft be carefully dried in the
open air, without being brought near the
fire, as a ftrong heat is not neceffary to pro-
duce the fulmination, and fri&ion alone is
fufficient for this purpofe : the vefTels which
contain it ought not to be clofed with glafs
ftoppers, but with cork ; the moft dreadful
accidents have (hewn that glafs ftoppers, by
the fri<£tion they produce in the necks of the
vefTels, expofe the operator to great danger,
from the fulmination of fuch particles of
the gold as may remain between the ftopper
and the neck. A terrible accident hap-
pened in the laboratory of M. Baume,
which is related in his chemiftry.

The opinions of chemifls have been vari-
ous refpe&ing the caufe of f he detonation of
fulminating gold. Baume fuppofed that a
nitrous fulphur, to which he attributes the
fulminating property, is formed in this ex-
periment $ but Bergman has (hewn that
this theory is not admifiible, iince he made
fulminating gold without the nitrous acid,
by diffolving a vitriolic precipitate of gold in
the acid, and precipitating it again by the
volatile alkali. Neither does the fulmina-
tion of gold depend on ammoniacal nitre,
iince this fait would certainly be wafhed off
by the addition of much water; and it is
not found that fulminating gold lofes its
property by fuch treatment. An attentive

examination

368 GOLD.

examination of the fulmination of gold
{hews, that it takes fire in the inftant that it
explodes ; if it be heated very gently, bril-
liant fparkles, fimilar to thofe of electricity,
are feen to efcape before its explofion. The
difcharge of an electric jar produces a deto-
nation, but a fimple ele&ric fpark does not.
Laftly, after the fulmination, the gold is
found in its metallic ftate. The fulmina-
tion of gold therefore appears to be pro-
duced by a combuftible matter ; and as al-
kaline gas is neceflary for the production of
this compound, it is at prefent acknowledged
that the explofion arifes from the volatile
alkali -, this theory is founded on the fol-
lowing fafts.

1 . M. Berthollet obtained alkaline gas, by
gently heating fulminating gold in copper
tubes, one extremity of which was plunged,
by means of a fyphon, beneath the mercury
of a pneumato-chemical apparatus ; after
this experiment the gold was deprived of
its fulminating property, and reduced to
calx.

2. By expofing fulminating gold to a de-
gree of heat, not fufficient to caufe it to
fulminate, Bergman deprived it of that pro-
perty by gradually volatilizing the alkaline
gas.

3. When a few grains of fulminating
gold are detonated in copper tubes, whofe
extremity is plunged beneath the mercury

of

GOLD. 369

of the pncumato-chemical apparatus, me-
phitis and a few drops of water are obtain-
ed, and the gold i^ reduced. M. Ekrthol-
let, the inventor of this experiment, thinks
that the volatile alkali is dtc< mpofed, that
its inflammable gas, uniting with the oxygi-
nous principle of the calx of gold, reduces
the calx by forming water, and that the
mephitis is fet at liberty ; the fulmination,
therefore, depends on the combination of
the inflammable gas and the difengagement
of the mephitis.

4. Concentrated vitriolic acid, melted
fulphur, fat oils, or ether, deprive gold of
its fulminating property, by feizing the
volatile alkali. A Angular property of ful-
minating gold, which (hews its powerful
action is, that when it is exploded on a
plate of metal, either lead, tin, or even
copper, it makes a mark or perforation in
it. Laftly, it does not appear capable of
taking fire in very rtrong and well clofed
veflels, fince it produced no explofion in an
iron ball well clofed and ftrongly heated.
This phenomenon appears to depend on its
being neceflary that a fpace fliould be left
for the difengagement of the mephitis.
Bergman, who was not well acquainted
with the nature of the gas difengaged
during the fulmination of this precipitate,
and who confidered it as pure air, together
with a fmall portion of volatile alkali, has
Vol. III. A a given

2JO GOLD.

given a fimilar explanation of the experi-
ments made by the Royal Society of
London.*

The folution of gold is precipitated by
liver of fulphur, while the fixed alkali
unites to the aqua regia; the fulphur which
falls down combines with the gold, but this
combination is by no means ftrong, for the
fulphur may be driven off, and the perfed:
metal left pure by the application of heat.
We muft here obferve, that gold precipi-
tated from aqua regia by any intermedium
whatfoever, is perfe&ly pure, even more fo
than gold purified by the procefs of parting ;
becaufe it is feparated from the filver it may
contain in this laft procefs, which may fall
down in the form of lunar cornea, and takes
place even during the folution of gold, as
we have before remarked.

Gold has not the ftrongeft affinity of any
metal with aqua regia; almoft all other
metallic fubftances, on the contrary, fepa-
rate it from its folvent : bifmuth, zink,
and mercury, precipitate gold ; a plate of
tin plunged in a folution of gold, Separates
the perfect metal in the form of a deep
violet powder, called purple precipitate of
Caffius. This precipitate, which is ufed
in painting in enamel and on porcelain,

* See the valuable differtation of this chemift on the
fulminating calx of gold, vol. II. of his Chemical EfTays.
London, 1784.

is

GOLD. 37I

is prepared by diluting a folution of tin in
aqua regia, with a large quantity of diftilled
water, and pouring in a few drops of the
folution of gold ; when the folutions are
well faturated, a red or crimfon precipitate is
immediately formed, which at the end of a
few days becomes purple : this precipitate
is light, and as it were mucilaginous ; it is
feparated from the liquor by filtration, warn-
ed and afterwards dried. It confifts of the
calces of tin and gold, and its preparation
is one of the mod fingular operations in
chemiftry, with refpect to the variety and
uncertainty it exhibits -, fometimes the pre-
cipitate is of a beautiful red, fometimes its
colour is a deep violet -, and, what is ftill
more aftonifhing, it frequently happens that
the mixture of the two folutions caufes
no precipitate whatever. Macquer, who
very carefully obferved thefe varieties, finds
that they depend almoft always on the ftate
of the folution of tin made ufe of; if the
folution has been made too rapidly, the
metal is too much calcined, and is contain-
ed in too fmall a quantity for the aqua regia
of the folution of gold to act on it; for it
is to the action of this la ft on the tin, that
he attributes the formation of the purple
precipitate of Caflius. In order to fucceed in
this operation, according to him, the folu-
tion of tin muft be made very flowly, and
in fuch a manner that it may contain the

A a 2 greateft

37^ GOLD.

greateft poffible quantity of metal not too
much calcined : on thefe principles he lays
down the following proceffes for making
purple precipitate. Pieces of tin are to be
diflolved in aqua regia, made of two parts
of fpirit of nitre, and one of fpirit of fait,
diluted with an equal weight of diflilled
water ; on the other hand, very pure gold
muft be diflolved by heat in an aqua regia,
Compofed of three parts of fpirit of nitre,
and one part of fpirit of fait; the folution
of tin is to be diluted in 100 parts
of diflilled water, and divided into two
portions ; to the firfl of the two, an addi-
tional quantity of water is to be added, and
each muft be tried with a drop of the folu-
tion of gold ; that which affords the moft
beautiful red colour muft be noted, and
the fame management adopted with the
others, after which the folution of gold
muft be poured in till it no longer occafions
any precipitate.

Lead, iron, copper, and filver have like-
wife the property of feparating gold from
its folvent ; lead and filver precipitate it of
a deep and dirty purple; copper and iron
feparate it with its metallic brilliancy; the
nitrous folution of filver, and that of mar-
tial vitriol, likewife occaiion a red or
brown precipitate from any folution of gold.
The affion of neutral falts on gold is not
perceptible; it is only obferved that borax,

fufecj

gold. 373

fufed with this metal, alters its colour, and
renders it remarkably pale, whereas nitre or
marine fait re-eftablifn the colour. The fo-
lution of borax poured into the folution of
gold, caufes a precipitate of fedative fait,
charged with particles of the metal.

Sulphur is incapable of uniting with gold,
and is advantageoufly ufed to feparate metals,
with which gold may be alloyed, more ef-
pecially filver: this alloy is melted in a cru-
cible, and flowers of fulphur, or fulphur in
powder, is thrown on its furface: the latter
fubftance, melting and combining with the
filver, floats above the gold in the form of
a blackilh fcoria. It muft be obferved, that
this operation, called dry parting, never
feparates the two metals accurately from
each oth£r, and that it is not ufed, except-
ing when the mafs of filver does not con-
tain a fufficient quantity of gold to repay
the expence of the operation of parting by
aqua fortis.

Liver of fulphur completely diflblves
gold. Stahl even thinks that this procefs
was ufed by Mofes, to render the calf of
gold adored by the Ifraelites foluble in
water: to form this combination, a mixture
of equal parts of fulphur and vegetable al-
kali muft be quickly fufed with one^eighth
part of the whole weight of leaf gold ;
this matter being poured out and levigated
on a (lone, forms, with hot diftilled water,
A a 3 a yel-

374 GOLD.

a yellowifh green folution, containing an
auriferous liver of fulphur ; the metal may
be precipitated by means of acids, and fepa-
rated from the fulphur which falls down
at the fame time, by heating it in an open
veffel.

Gold combines with moft metallic fub-
fiances, and exhibits many important phe-
nomena in its combinations.

It unites with arfenic, and forms a brittle
pale compound* the laft portions of arfenic
are very difficultly feparated from this alloy
by the aftion of heat; the gold feems to
communicate fixity to it.

The alloy of cobalt with gold has not
been examined.

It unites with bifmuth, which renders it
brittle, as do likewife nickel and the regu-
lus of antimony > as thefe femi-metals are
very calcinable, and, for the moft part, fufi-
ble, they are eafily feparated from gold by
the combined adtion of fire and air.

Crude antimony has been greatly extolled
by the alchemifts for the purification of
gold; when this fubftance is melted with
gold, alloyed with other metallic fubftances,
as copper, iron, or filver, the fulphur of
the antimony unites to the alloy, and fepa-
rates them from the gold, which is found
at the bottom of the veffel ; this gold is
contaminated with regulus of antimony,
and muft be purified by a white heat ;

the

GOLD. 275

the regulus of antimony, by this treatment,
is volatilized, but the laft portions require
a very ftrong heat to drive them off. It is
likewife obferved that the femi -metal car-
ries up certain portions of gold in its vola-
tilization. This procefs, fo celebrated by the
alchemifts, has not, therefore, any advan-
tage over that in which fulphur is employed
alone.

Gold readily unites with zink ; the pro-
duel: is a mixed metal, more brittle and
white in proportion as the quantity of femi-
metal is greater; this alloy, made with
equal parts of each metal, is of a very fine
grain, and takes fo beautiful a polifh, that
it has been recommended by Hellot to make
mirrors of telefcopes, not being fubjeel: to
tarnifh. When the zink is feparated from
the gold by calcination, its flowers are
reddifh, and carry up a fmall quantity of
gold with them, as Stahl has obferved.

Gold has a ftronger affinity with mercury
than with other metallic fubflances, and is
capable of decompofing their amalgams ; it
unites with mercury in every proportion,
and forms an amalgam which is more folid,
and of a darker colour, in proportion as
the quantity of gold is greater ; this amal-
gam liquifies by heat, and cryftallizes by
cooling, as do moft compounds of this na-
ture; it is not well known what regular form
it takes. M. Sage affirms, that the cry-

A a 4 ftals

376 GOLD.

ftals refemble plumofe filver, and, by the
magnifier, appear to be quadrangular prifms.
He likewife afferts, that the mercury ac-
quires fixity in this combination. This
amalgam is employed in water-gilding.

Though gold is nut c pable of calcina-
tion by the action of the rire of our furnaces
with accefs of air, it neverthelefs becomes
calcined when heated together with mercury:
if mercury with one forty-eighth of its
weight of gold, be heated in a flat-bottom-
ed matrafs, whofe n ck is drawn out into a
capillary tube, in the fame manner as is
done in the preparation of the calx of mer-
cury, called precipitate per fe, the two
metallic fubftances become calcined at the
fame time, and are converted into a deep
red powder. This compound calx, accord-
ing to Baume, is obtained in much lefs time
than that of mercury alone. We here fee a
metal, which, though very difficult to cal-
cine alone, affiftsand facilitates the calcina-
tion of another metallic matter, which is
likewife very difficultly calcined.

Gold is eafily alloyed with tin and lead ;
thefe two metals deprive it of all its duc-
tility; its alloy with iron is very hard, and
may be ufed to form cutting instruments,
much fuperior to thofe made with pure
ileel : this mixture is grey, and attracted
by the magnet. Lewis propofes gold as a

very

gold. 377

very proper and firm folder for fmall pieces
of fteel.

Gold combines with copper, which gives
it a red colour, and greater firmnefs, at the
fame time that it renders it more fufible :
this alloy is mixed in different proportions
for money, plate, and toys. Laftly, gold
is alloyed with filver, which deprives it of
its colour, and renders it very pale : this
alloy is not, however, made without a
certain degree of difficulty on account of
the different fpecific gravities of thefe two
metals, as Homberg obferves, who faw them
feparate during their fufion. The alloy of
gold with filver forms the green gold of the
jewellers and gold-beaters.

As gold is of the mofl extenfive ufe, and
by the convention of mankind, is become,
together with ulver, the price of all the
other productions of nature and of art ; it
is of importance to afcertain the degree of
purity of this precious metal, in order to
prevent the deceptions which covetoufnefs
might produce, and to caufe the value of
all the maffes or pieces of gold, difperfed in
commerce, to be the fame, equal weights
being fuppofed. Severe laws, founJed in juf-
tice, have therefore been made, eftabliftung the
quantity of alloy neceffary to be ufed, in order
to give the due degree of hardnefs and rigidity
to gold intended to form utenrils, in which
thefe properties are neceffary. Chemiftry

affords

378 GOLD.

affords methods of afcertaining the quantity
of imperfect metal mixed with gold : the
operation by which this knowledge is ob-
tained, is called the affay of gold. Twenty-
four grains of the gold intended to be
affayed, is cuppelled with forty-eight grains
of filver and four drams of pure lead ; the
latter, in its vitrification, carries along with
it the imperfect metals, fuch as copper, &c,
and the gold remains' comoined with the
filver : after the cuppellation is finifhed,
thefe two metals are feparated by an opera-
tion, called parting; the parting of gold and
filver confifts in the feparating of the two
metals by a folvent, which acts on filver
without affecting gold : aqua fortis is com-
monly ufed. Silver is added to the gold,
becaufe experience has fhewn, that it is
neceffary the gold fhould be mixed with at
leaft double its weight of filver, in order that
the nitrous acid may perfectly diffolve the
latter metal. As three parts of filver are
ufually added to one of gold, this procefs
is called quartation ; the gold being one-
fourth of the weight of the alloy.

The metallic button being hammered flat,
and care being taken to heat it from time to
time, left it fhould become hard and break in
pieces, and fome part fly away, and be loft ;
it is then rolled up in a fpiral form, and
put into a fmall matrafs, with five or fix
drams of precipitated aquafortis, in which

there

gold. 379

there is no mixture of the muriatic acid, and
which has been previoufly diluted with half
its weight of water : a gentle heat is applied
till the effervefcence has taken place ; the
filver becomes diffolved, and the metallic
coil aflumes a brown colour. When the
action of the acid has ceafed, it is decanted
off; the fpiral piece of metal which is now
become very thin and porous, is wa/hed with
water, and put into a crucible, together
with the water,- the water is then decanted
off, the crucible made red hot, and the gold
is found pure with all its metallic properties :
by the weight of the gold, the quantity of
alloy it originally contained is known. To
afcertain with precifion the quantity of im-
perfedt metal which the gold may contain, a
given mafs of gold is fuppofed to contain
twenty four parts, called carats ; and, for great
exaftnefs, each carrat is divided into thirty-
two parts, called thirty feconds of a carrat :
if the gold after the affay has loft one grain
out of twenty-four, it is gold of twenty-
three carrats •> if it has loft one grain and a
half, it is gold of twenty carats fixteen
thirty-feconds, and fo forth. The weight
ufed in the allay of gold, is called the affay
weight, and ufually confifts of twenty-
four grains ; it is divided into twenty-four
carats, which are likewife fubdivided into
thirty-two parts : an affay weight, which
weighs twelve grains, is likewife ufed, but

divided

38Q GOLD.

divided into twenty-four carats, and the
carat, into thirty-two thirty feconds.

There are two important obfervations ne-
ceffary to be made, refpeciing the operation
of parting.

1. Some chemifts have thought that the
nitrous acid diflblves a fmall quantity of
gold with the filver. M. Baum^ has ob-
ferved, pages 117 and n8, of the third vo-
lume of his chemiitxy, that the filver ob-
tained in the operation of parting, contains a
notable quantity of gold. Out of two pounds
of fine grain filver, ufed by this chemiit, to
make lapis infernalis; he affirms, that he
has ufually feparated near half a drachm of
gold in the form of a black powder ; how-
ever, when the parting is made with an acid
not too much concentrated, and the folution
is not carried too far, the gold remains pure
and untouched, and the lilver contains no
portion of that metal. The gentlemen of
the chemical clafs of the academy, were di-
rected by adminiftration, to examine whe-
ther, in the procefs of parting, the nitrous
acid diffolves gold -y they made a great num-
ber of.experiments, from which they con-
cluded, that in the operation of parting, ac-
cording to the received rules and ufage, there
can never be the fmalleft lofs on the gold,
and that this operation may be confidered as
perfect. This deciiion, extracted from the
report publifhed by the academy, is well

calculated

GOLD, 381

calculated for the information of the pub-
lic, and the eftablifliment of commercial
confidence refpe&ing this fubjeft.

2. Many dccimaftic philofophers, and
amoneft others Schindler and Schlutter, have
thought that the coil of gold, after parting,
retained a fmall quantity of filver ; to this
portion they gave the name of furcharge, or
interhalt. Me firs. Hellot, Macquer, and Til-
let, who were commiflioned to examine the
operation of the afiayers of money, have
proved, that it does not contain filver; yet
M. Sage affirms in his work, intitled, L'Art
d'effayer Tor et l'argent, page 64, that this
gold always retains a fmall proportion of
filver, and that it may be exhibited by dif-
folving the metal in twelve parts of aqua
regia, the cold folution depofiting, at the
end of a certain time, and often, even twelve
hours after it has been made, a fmall quan-
tity of luna cornea, in the form of a white
powder.

Gold is applied to a great number of ufes;
its fcarcity and price prevent its being made
into utenlils, or vefTels ; but as its brillian-
cy and colour are very agreeable, methods
have been found of applying it to the fur-
face of a great number of bodies, which it
at the fame time defends from the impref-
fions of the air.

This art, in general called gilding, is per-
formed in a variety of methods. Leaves of

gold

382 GOLD.

gold are often applied on wood by means of
fome glutinous fubftance. A powder of
gold is prepared by triturating the clippings
of gold leaf with honey, wafliing the pafte
with water, and drying the particles of gold,
which precipitate. Shell gold is the laft
mentioned preparation, mixed with a muci-
laginous water, or folution of gum. The name
of gold in rags is given to the following pre-
paration : rags are fteeped in a folution of
gold, and afterwards dried and burned for
ufe ; a wet cork is dipped in thefe aflies, and
rubbed on filver, upon which the minutely
divided gold eafily applies itfelf. We have
already fpoken of water-gilding; this is
done by previoufly cleaning a piece of cop-
per, intended to be gilt, with fand, and
weak aqua fortis, called aqua fecunda, after
which the piece is plunged in a diluted folu-
tion of mercury; the mercury which preci-
pitates, caufes the amalgam of gold to ad-
here ; which is fpread on the piece, after
having wafhed it with water to carry off the
acid : when the amalgam is uniformly fpread,
the piece is heated on charcoal, to volatilize
the mercury, and the work is finished by
covering it with gilder's wax, compofed of
red bole, verdigrife, alum or martial vitriol,
incorporated with yellow wax, and heated
once more to burn off the wax.

The other ufes of gold, for toys, laces,
&c. are fufficiently known without enume-
ration.

PLATINA. 383

ration. As to the medicinal virtues attri-
buted to gold, it is admitted by all phyfi-
cians of reputation, that they are imaginary,
and that the effefts of the different kinds of
potable gold propofed by the alchemifts,
arife from the fubitances in which the metal
has been mixed or diflblved,

CHAP. XXL

Concerning Platina.

T) LATIN A, which has not been known
•*• as a peculiar metal for more than four-
teen years, has been hitherto found only
in the gold mines of America, more efpe-
cially in thofe of Santa Fe, near Cartha-
gena, and in the Bailywick of Choco in Peru.
The Spaniards give it this name from the
word plata, which fignifies filver in their
language, by way of comparifon to that
metal, whofe colour it imitates. The name of
white gold however appears to agree better
with its properties than that of little filver,
becaufe it in fact refembles gold much more
than filver in mofl of its properties. Some
toys made of platina were in exiftence be-
fore the time we have cited ; but as this
metal cannot be melted and wrought alone,
it is probable that the fhuff boxes, heads of

canes,

384 PLATINA.

canes, and other utenfils of this kind, which
were fold under the name of platina, were
alloys of this metal with certain metallic
fubftances, which might give it fufibility,
as we mall fee in the hiftory of its alloys.

The platina, in mineralogical collections,
has the form of fmall grains, its plates of a
blueifh black, whofe colour is intermediate
between thofeof filver andiron. Thefe grains
are mixed with many foreign fubftances ;
they contain fmall particles of gold, black-
ifh ferruginous fandy grains which by the
magnifier appear fcorified, and certain par-
ticles of mercury ; the mercury is feparated
from this mixture by heating; wafhing car-
ries off the fand, and grains of iron, which
may likewife be feparated by the magnet;
after which the particles of gold and grains
of platina only remain, which are eaiily fe-
parated according to Margraaf. If the grains
of platina be examined by the magnifier,
fome appear regular, others round and flat,
like a kind of button. When beat on the
anvil, moft of them are flattened, and appear
duftile ; fome break into leveral pieces ; the
latter examined more narrowly, appear to
be hollow, and particles of iron" and a white
powder has been found within them. The
property of being attradi ct by the magnet,
which thefe grains poffefs, though accu-
rately feparated from the ferruginous fand
they contain, muft doubtlefs be attributed

to

PLATINA. 385

to a portion of iron contained within
them.

The hardnefs of this metal nearly ap-
proaches to that of iron ; the fpecific gra-
vity of platina, mixed with all the foreign
matters we have fpoken of, nearly approaches
to that of gold ; it lofes in water between
one fixteenth and one eighteenth of its
weight. Meffrs. de Buffon and Tiliet com-
pared together an equal volume of pla-
tina, and of gold reduced into particles fimi-
lar to thofe of the platina, and found that the
fpecific gravity of the former was about one
twelfth lefs than the gold; when purified
by fufion, it approaches to the fpecific gra-
vity of gold.

It is not probable that platina exifts in its
ores in the fame form as it comes to us,
but that its granular or plated figure, is pro-
duced by the motion of the waters by which
it is carried from the mountains to the
plains. It has been fometimes found in
maffes of confiderable magnitude ; the fo-
ciety of Bifcay poiiefs one of the iize of a
pigeon's egg. As it is found in the neigh-
bourhood of gold mines, it is always mixed
with a quantity of this metal. The mer-
cury it contains is part of that ufed in ex-
tracting the gold. Though toys made of
platina have been long fold, this metal was
not diftinguifhed as a peculiar fubftance till
lately : the workmen paid no particular at-
Vol, III. B b tention

386 PLATINA.

tention to it, and appear to have fet no value
on it, becaufe of its dull afpect, and the dif-
ficulty of treating it. The firft perfon who
paid any particular attention to platina, was
a Spanifli mathematician, Don Antonio
Ulloa, who accompanied the French Aca-
demicians in the celebrated expedition to
Peru, for determining the figure of the
earth. This philofopher gives a curfory
account of it in the relation of his voyage,
publifhed at Madrid in the year 1748.
Charles Wood, an Englifh metallurgift,
brought a quantity of this metal from Ja-
maica, in the year 1741, which he after-
wards examined, and gave an account of his
experiments in the Philofophical Tranfac-
tions for the years 1749 and 1750: at this
aera, the greater! chemifts in Europe appear-
ed emulous in their inquiries refpecling this
new metal, which promifed, by its fingular
properties, fuch confiderable advantages.
Scheffer, a Swedifh chemift, publifhed his
experiments on platina in the Memoirs of the
Academy of Stockholm, in the year 1752.
Lewis, an Englifh chemift, made a connected
and almoft complete feries of experiments on
this metal, which may be found in the Philo-
fophical Tranfactions for the year 1754.
Margraaf has inferted in the Memoirs of the
Academy of Berlin for 1757, an account of his
experiments on this new metal. Moft of thefe
Memoirs were collected by Mr. Mforin, in
a work intitled La platine, L'or blanc, ou le

huitierne

PLATINA. 387

huitieme metal : Paris, 1758. At the fame
time Mefi'rs. Macquer and Baume made, in
conjunction, a great number of important
experiments on platina, which were pub-
lished in the Memoirs of the Academy for
the year 1758. M. de Buffon has given
an account in the firft volume of the fup-
plement to his Natural Hiftory, of a feries
of inquiries refpedting platina made by
himfelf, M. de Murveau, and the Count
de Milly. The Baron Sickengen has like-
wife made a feries of experiments on this
metal ; his work has not yet been publifhed,
but Macquer has given an extract of it in his
Dictionary of Chemiftry. M. de L'Ifle has
communicated to the academy, certain ex-
periments made by himfelf on platina. The
fcarcity of this metal, and the difficulties at-
tending the experiments made on it, {topped
for a time theprogrefsof inquiries, but within
the laft few years they have been re fumed with
new fpirit. Bergman, Achard, and de Mor-
veau, have exerted themfelves in the ex->
amination of the properties of this metal.

Platina purified and feparated by wafhing,
trituration, and by the muriatic acid, from
the foreign bodies it may contain, and after-
wards expofed to the mod violent heat of
a furnace, is not altered, but its parts flight—
ly adhere together. All the chemifts who
have made experiments on this metal, agree
in this refpedt. MeiTrs. Macquer and
Baume kept it for feveral days expofed to
B b 2 ^ the

3S8 PLATINA.

the continual fire of a glafs-houfe, without
any other alteration, than that its grains
were flightly adherent to each other; but
this agglutination was fo flight, that they
feparated even by touching. They obferved>
that in thefe experiments the colour of the
platina became brilliant by a white heat;
that it acquired a dull, and greyifh colour
after it had been heated a long time ; and
laftly, that its weight was conftantly in-
creafed as Margraaf had afcertained, which
could only arife from calcination. Thefc
chemifts expofed platina to the focus of a
large burning mirror 3 it firft fmoked, then
emitted very lively fparks, and laftly, thofe
portions which were expofed to the centre
of the focus, melted in the fpace of a mi-
nute. The melted portions were of a white
brilliant colour, in the form of a button ;
they could be cut into pieces with a knife ;
one of thefe maffes was flattened on the anvil,
and converted into a thin plate, without
cracking or breaking, but it became hard
under the hammer. This valuable experi-
ment fhews, that platina is fufible by a
fire of the utmoft violence, that it is as mal-
leable as gold and filver, and that it is fcarcely
alterable by the a&ion of fire; for in all
thefe experiments, mofl of which were made
in the open air, the platina exhibited no ap-
pearance of calcination. M. de Morveau
has likewife fucceeded in melting platina
in the wind furnace defcribed by Mr. Mac-

quer,

PLATINA.' 3S9

quer, by means of his own reducing flux,
compofed of eight parts of pounded glafs,
one part of calcined borax, and half a part
of charcoal in powder. Small portions
alone, and without addition, are now very
eafily melted, by heating them on a lighted
charcoal, with a ftream of vital air ^ but
thefe fmall ductile globules cannot be ap-
plied to any ufe, on account of their incon-
siderable fize.

Platina, when expofed to air, is not at all
changed; it is not however known what
alteration it may be fufceptible of, if kept
red hot for a long time with contadt of air :
perhaps it might be calcined, as Junker
affirms gold and filver are, when treated
in the fame manner.

This metal is not altered by water, earth,
the metals, the falino-terreftrial fubftances,
or by alkalies. The moil concentrated vitri-
olic, nitrous or muriatic acids do not aft on
platina, even when boiling; neither is diftilla-
tion, which is known to be fo efficacious in
promoting the adtion of acids on metallic fub-
ftances, of any advantage in the prefent cafe.
The vitriolic acid limply tarniffies the grains
of platina, according to Lewis and Baume;
the nitrous acid, on the contrary, renders
them brittle. Margraaf affirms, that towards
the end of the diftillation of this acid from
platina, he obtained a fmall quantity of
arfenic, a phenomenon not obferved by
other chemifts. The muriatic acid produced

B b 3 no

o'9° PLATINA.'

no change whatfoever in grains of platina.
M?rgraaf likewife obtained from this acid,
diflilled from the metal, a white fublimate,
which appeared to him to be arfenic, and a
reddifh fublimate, whofe properties he could
not examine on account of its being in fp
fmall a quantity. All thefe appear, how-
ever, to be foreign to the platina itfelf : this
metal therefore refembles gold by the flight
action of the fimple acids upon it; but the
analogy isftill moreevidentby itsfolubility ia
the aerated muriatic acid, and in aqua regia,

The firft of thefe acids diffolves platina
with facility, and without the afliflance of
3 ftrong heat; feventy or eighty degrees of
heat in the atmofphere being fufficient to
facilitate this folution, which takes place
without any fenfible effervefcence, and in
other refpecls does not differ from the fol-
lowing,

The aqua regia be ft adapted to diffolve pla-
tina, iscompofed of equal parts of the muria-
tic and nitrous acids. To effect this folution,
which in general is lefs eafily performed than
that of gold, one ounce of platina muft be
put into a retort, on which a pound of aqua
regia, in the proportions here mentioned
muft be poured ; the retort is then to be
placed on a fand bath, with a receiver ap-
plied as foon as the acid is hot : a few bubbles
of nitrous gas are extricated, and the action
of the aqua regia proceeds without violence
qr rapidity: the colour of the fluid becomes

at;

platina. 39r

at firfl: yellow, afterwards orange, and at
lafl of a very deep brown. When the folu-
tion is finilhed, reddiih and black particles
of land are found at the bottom of the
retort, from which the faturated liquor is to
be feparated by decantation: imall irregular
cryflals of a dufky colour are gradually de-
poiited, which coniiil of a combination of
the acid and platina. The folution of platina
is of a deeper colour than that of any
other metal. Though it appears of a dark
brown, yet, if it be diluted with water, it
aiTumes firfl an orange colour, which foon
becomes yellow, and refembles the folution
of gold : it tinges animal matters of a
blackifh brown, not at all inclining to pur-
ple. M. Baume affirms, that platina fufed
in the focus of a burning mirror, and dif-
folved in aqua regia, does not affume a brown
colour, like that of platina in grains, but
that the folution is of a deep orange yellow
colour.

Macquer affirms, that by evaporating and
cooling the folution of platina, much larger
and more regular cryflals are obtained, than
thofe fpontaneoufly depofited by the fatu-
rated fluid. Lewis having left this folution
to evaporate in the open air, obtained cry-
flals of a deep red, of a moderate fize, ir-
regularly formed, and refembling the flowers
of benzoin, though thicker : Bergman de-
fcribes it as being of an octahedral form. This
iritis fharp, but'fcarcely cauflic; it melts in

B b 4. the

392 PLATINA.

the fire, the acid being diflipated, and a re-
fidue is left in the form of an obfeure grey
calx. Concentrated vitriolic acid occafions a
precipitate of a deep colour, which, doubt-
lefs, is a vitriol of platina; the muriatic
acid, in a certain time, produces a yellowifh
depoiition.

Alkalies and the falino-terreftrial fub-
flances decompofe the folution of platina,
and precipitate the metal in the form of
calx : the cretaceous vegetable alkali pro-
duces an orange coloured precipitate, in the
folution of platina, which is not a pure
calx. Meffrs. Macquer and Baume have
obferved that its colour is owing to a cer-
tain quantity of acid it contains. It muft
therefore be confidered as a mixture of a
portion of the calx of platina, with mu-
riate of pot-am, or as a kind of triple fait.
This opinion is proved by warning the pre-
cipitate with hot water; for the fluid then
becomes coloured by diffolving the fait of
platina, and'the refidue, which is a pure calx
of the metal, is grey. Fixed alkali, boiled
on this precipitate, quickly deprives it of
its colour, and leaves a calx of platina,
which is of a pearl colour, according to the
experiments of M. Baume : this chemift
was convinced that the precipitate of pla-
tina is foluble in the alkali, becaufe a folu-
tion of the metal, dropped into an hot
folution of cretaceous vegetable alkali, af-
forded no precipitate. For this reafon, it is

that

PLATINA. 393

that the folution precipitated by fixed alkali
always retains a deep colour, and affords pla-
tina by evaporating it to drynefs. Margraaf
has discovered that foda does not precipitate
the folution of platina, but Bergman has
obferved, that on the addition of a confi-
derable quantity of that alkali a precipitate
is readily afforded.

Alkalies faturated with the colouring
matter of Pruffian blue, form an abundant
blue precipitate, which, according to M.
Baume, arifes from the iron contained in
the alkali ; fi nee Pruffian blue deprived of
the iron it contains, by the procefs directed
by that chemift, does not afford more than
a few particles of blue, with the folution
of platina, which arife from the fmall
portion of iron always contained in that
metal. Bergman affirms that the Pruffian
lixivium, well faturated and very pure, does
not precipitate the folution of platina; and
that this metal is the only one not precipi-
tated by the Pruffian lixivium; he, therefore,
propofes that lixivium to feparate from the
iron which it always contains.

The cauftic volatile alkali precipitates
platina of an orange yellow: this precipitate
is almoft intirely faline; water diffolving the
greater!: part, and becoming coloured like a
folution of gold. After the aftion of water
on this precipitate, a blackifh fubftance,
which appears to be ferruginous, remains.
The precipitate of platina by volatile alkali,

differs

394 PLATINA.'

differs from that of gold in its not pofleffing
the fulminating property of the latter.

Nut-galls precipitate the folution of pla-
tina of a deep green colour, which gradually
becomes lighter by ftanding.

All the precipitates obtained from the
folution of platina by the addition of alka-
line fubftances, are not capable of being vitri-
fied, or of colouring glafs. In the trials of
Lewis andBaume, on this fubjecft, the platina
was conftantly reduced in grains, in ramifica-
tions, or a kind of checquer work. A fort of
button of platina may be obtained by ex-
pofing thefe precipitates to a ftrong heat,
with certain reducing fluxes, as borax,
cream of tartar, glafs, &c. MefTrs. Mac-
quer and Baume fucceeded in this manner
by a forge fire, urged by two pair of ftrong
bellows, to melt in thirty-five minutes, a
precipitate of platina mixed with fluxing
fubftances : they obtained, beneath a hard
blackifh glafs refembling that of bottles,
a button of platina, which appeared to have
been well fufed: this button was not duc-
tile, but broke into two pieces, and appear-
ed to be hollow ; its fra&ure was grained,
and its hardnefs nearly equal to that of
forged iron, as it made deep traces in gold,
copper, and even in iron. Though we have
affirmed that the precipitates of platina do
not appear to be verifiable or capable of tinging
glafs, yet M. Baumc has fucceeded in melt-
ing them intoavitriformfubftance by two dif-
ferent

PLATINA. 395

ferent procefles. The precipitate of platina,
mixed with calcined borax, and a very fufi-
ble white glafs, was expofed for thirty-fix
hours in the hotteft part of a potter's furnace,
and afforded a greenifh glafs, inclining to
yellow, without globules of reduced metal.
This glafs treated a fecond time with cream
cf tartar, gypfum, and vegetable alkali,
was completely melted, and exhibited
globules of platina difperfed through their
lubftance. M. Baume feparated them by
warning, and found them ductile. The fame
chemift afterwards, together with M*
Macquer, expofed precipitate of platina to
the fame burning mirror with which they
had fufed the metal : the precipitate ex-
haled a very thick and luminous fume, with
a ftrong fmell of aqua regia ; it loft its red
colcur, refumed that of platina, and melted
into a perfect brilliant button, which was
found to be an opake vitreous fubftance, of
an hyacinthine colour at its furface, and
blackifh within, and may be confidered as
a true glafs of platina'. It may however be
obferved, that the faline matters with which
it was impregnated, contributed doubtlefs
to its vitrification.

The precipitate of platina does not appear
to be foluble in fimple acids, but it diflblves
very wTell in aqua regia, to which it gives
an orange colour, not at all refembling the
brown colour exhibited by the platina in
grains.

The

396 PLATINA.

The folution of platina is not precipitat-
ed by the alkaline or perfect neutral falts ;
but fal-ammoniac precipitates it abundant-
ly. The rationale of this experiment is not
well decided. The orange-coloured preci-
pitate obtained, by pouring a folution of
fal-ammoniac into a folution of platina, ap-
pears to be a faline fubftance, intirely folu-
ble in water; this precipitate has a valuable
property, difcovered by M. de L'Ifle, viz.
that it is fufible without addition, in a
good furnace or common forge heat. The
platina melted by this procefs is a brilliant
denfe and clofe grained button ; but it is
not malleable, unlefs it has been expofed to
a very ftrong heat, Macquer thinks that this
fulion, like that of the grains of platina ex-
pofed alone to the a&ion of a violent fire,
conlifts only in the agglutination of the
foftened particles, which being exceedingly
more divided and minute than the grains of
platina, adhere to and touch each other in a
greater number of points than the grains ;
and in that manner render the texture of the
metal much more clofe, though no true
fufion may have taken place. It feems,
however, that if platina in grains be capable
of fufion by the burning glafs, and of be-
coming confiderably dudtile, the precipitate
of this metal made by fal-ammoniac, may
likewife be fufed on account of its extreme
divifionj and that its not being as duftile as

the

PLATINA. 397

the button of platina fufed by the folar heats
may perhaps depend on its flill retaining a
part of the matter it carried down with it
in its precipitation, of which it may be
poffible to deprive it by fire.

Margraaf diffolved platina in an aqua re-
gia compofed of fixteen parts of nitrous
acid, and one of fal-ammoniac ; by dial-
ling this folution to drynefs, and heating
the bottom of the retort till it was red, a
fait of a deep red colour was fublimed, and
the reiidue was in the form of a reddifh
powder. It is not known whether the fo-
lution of platina in fimple aqua regia, made
with the nitrous and marine acids, will
afford a fublimate of the fame kind by dif-
tillation.

Meffrs. Margraaf, Baume, and Lewis,
mixed the folution of platina with folutions
of all the other metallic fubftances , the re-
fult of their experiments was, that almoft
all the metals precipitate platina in the
form of a brick-duft coloured powder, and
that none of thefe precipitates poflefs the
metallic properties, as happens with moft of
the other metals. This exhibits another ana-
logy between gold and platina, though the
latter does not afford a purple precipitate
with tin, but a brown precipitate, inclining
to red. With regard to the effect of the differ-
ent metallic folutions on that of platina, it
need only be obferved, that the folutions of

bifmuth

39$ t>LAT[NA.

bifmuth and lead by the nitrous acid, of iron
and copper by different acids, and of gold
by aqua regia, do not produce any precipi-
tate in that of platina, according to Mar-
graaf; but that on the contrary, thofe of
the arfenical neutral fait, of zink and of fil-
ver, by the nitrous acid, precipitate it ; the
firft in the form of a cryftallized fubftance,
in fmall quantity, and of a beautiful gold
colour ; the fecond in a red orange coloured
matter, and the third in a yellow matter.
Thefe different precipitates have not yet been
well examined ; and the decompofition by
which they are occafioned is unknown.

Moft of the neutral falts have no action
on platina. Margraaf heated platina by a
flrong fire, with vitriolated tartar and Glau-
ber's fait ; thefe falts melted, and the pla-
tina remained in grains without alteration :
it only communicated a flight reddifh co-
lour to the faline fubftances, doubtlefs on
account of the iron communicated by the
metal to them.

Nitre produces a lingular alteration in
platina, according to the experiments of
Lewis and Margraaf. Though no detonation
is produced when a mixture of both fub-
ftances is thrown into a red hot crucible;
yet, by a ftrong heat long continued, fuchas
Lewis applied for three fucceffive days and
nights to a mixture of one part of platina and
two of nitre, the metal becomes of a rufty

colour*

PLATINA." 399

colour. If the mixture be boiled in water,
the fluid diflblves the alkali, which takes «up
the brownifh powder, and the platina fepa-
rated from the liquid is found diminished
more than one-third of its weight. The
brown powder taken up by the alkali may
be feparated by filtration. It appears to
be a kind of calx of platina, mixed with a
fmall quantity of faffron of Mars. Lewis
converted this calx to a whitifh grey colour,
by diftilling it a great number of times
with fal ammoniac. Margraaf, who repeated
this experiment, adds two important fad:s ;
the firft is that platina combined with
the alkali of nitre, and diluted in a certain
quantity of water, forms a jelly; and the
other, that by calcining the portion of
metal feparated from the jelly, diluted with
water and filtrated, it becomes of a black
pitchy colour. This experiment certainly
(hews a great alteration of the platina, and
requires to be continued, in order to decide
whether by virtue of repeated calcinations
with nitre it be poffible to reduce the whole
of the metal into a brown powder, and
efpecially to determine the ftate of the pla-
tina thus calcined.

Marine fait, febrifuge fait, borax, and
the earthy falts, produce no change in
platina, nor facilitate its fufion ; fal ammo-
niac, diftilled with this metal, affords a
fmall quantity of martial flowers by virtue

of

400 PLATINA.

of the iron it contains. Chemifts are not
agreed refpe&ing the mutual action of arfe-
nic and platina. Scheffer firft aflerted, that
arfenic caufes this metal to enter into
fufion ; but the experiment fucceeded but
imperfectly in the hands of Lrwis, and
not at all with Margraaf, Macquer, and
Baume. This experiment has been fince
repeated, and it appears that platina is in
fad very fufible with arfenic, but that it re-
mains brittle. In proportion as the arfenic
is driven offby a continuance of heat, ^.be-
comes more ductile, and by this procefe it
is, that M. Achard and M. de Morveau
fucceeded in making crucibles of platina,
by melting it a fecond time in moulds. No
one has attempted to combine cobalt, nickel,
or manganefe with platina.

This perfect metai unites very well with
bifmuth, which renders it fo much the more
fufible, as the quantity of the latter is great-
er; the alloy is brittle, and becomes yellow,
purple, and blackifh i;i the air. This mixed
metal cannot be cuppelled without the
greateft difficulty, and never forms a mafs of
any confiderable ductility.

Platina fufes readily with regulus of an-
timony, and produces 3 brittle metal of a
plated texture, from which the regulus may
be feparated by the aftion of fire, though
not fo completely, but that the platina al-
ways retains a iiifficient quantity to render

it

PLATINA. 401

ft defe&ive in weight and duftility. Zink
renders platina very fufible, and combines
readily with it : this alloy is brittle, and
difficult to file; its colour is blueifh. When
the platina is moft abundant, thefe two me-
tallic fubftances are feparated by the adtion
of fire, which volatilizes the zink, though
the platina always retains a fmall portion.

Platina does not unite with mercury,
though triturated for feveral hours with that
metallic fluid. It is likewife known, that
platina refifts the mercury ufed in America
to feparate the gold. Many intermediums,
fuch as water, ufed by Lewis and Beaume,
and aqua regia by Scheffer, have not been
found to facilitate the union of thefe two me-
tals. In this refpedt platina appears to re-
femble iron, to whofe colour and hardnefs it
likewife in fome refpedts approaches.

Platina mixes very eafily with tin> and
forms a very fufible and fluid alloy. It is
brittle, fo as even to break by a fall when
the two metals are united in equal portions.
When the tin is in the proportion of twelve
or more to one of platina, the mixture is con-
fiderably dudtile, but its grain is coarie, and
it becomes yellow in the air. Platina re-
markably diminiihes the dudtility of tin, and
the alloy does not promife to be of any ufe ;
yet when it is well polifhed, it may remain
long expofed to the air without alteration.
It feems that Lewis, to whom we are in-

Vol. III. C c debted

402 PLATINA.

debted for moft of the knowledge we poflefs
refpecting the alloys of platina, fucceeded
in calcining this metal, and diffolving it in
the muriatic acid by means of tin.

Lead and platina unite very well by fufion;
but they require a ftronger heat than the laft
mentioned alloy. Platina deprives lead of
its ductility ; the combination of thefe twq
metals is of a purplifli colour, and brittle,
according to the proportions of platina, fili-
ated and granulated in its fracture, and
quickly changes by expofure to air. Cup-
pellation with lead, was one of the firft and
moft important experiments attempted to be
made with platina ; becaufe this operation
was expected to deprive it of the foreign me-
tallic fubftances it might contain. Lewis,
and feveral other chemifts, have in vain at-
tempted to cuppel platina in the ordinary
cuppelling furnaces, though they applied a
moft violent heat. The vitrification and ab-
forption of the lead takes place as ufual at the
commencement of the procefs, on account of
the excefs of that metal ; but the platina
foon becomes fixed, and the operation is at
an end. The metal remains united with a
portion of the lead, and is not at all duc-
tile. Meffrs. Macquer and Baume, fuc-
ceeded in the perfect cuppellation of platina,
by expofing an ounce of the metal, and two
ounces of lead, in the hotteft part of the
porcelain furnace at Seves. The wood fire
^ lafts

PLATINA. 403

lafts for fifty hours fucceffively ; at the end
of this time the platina was found flattened
on the cuppel ; its upper furface was dull
and rough, and eafily Separated; its under
furface was brilliant, and, what is the moft
valuable, it was eafily extended under the
hammer. Theie chemifts were convinced, by
every poffible method, that the platina did
not contain lead, but was very pure. M.
de Morveau likewife fucceeded in cuppelling
a mixture of one drachm of platina, and two
drachms of lead, in the wind furnace of
Macquer : this operation, made at four fuc-
ceffive times, lafled eleven or twelve hours.
M. de Morveau obtained a button of platina,
not adhering to the cuppel, uniform, of a
colour refembling tin, but rather rough,
which weighed exadtly one drachm, and was
found to be not at all adted on by the mag-
net. This procefs appears to be excellently
adapted for obtaining platina in plates or
laminae, which may be forged, and confe-
quently may be employed in making various
utenlils of great value, with refpedt to hard-
nefs and unchangeablenefs. M. Baume has
likewife oblerved another very ufeful pro-
perty, viz. that of welding and forging to-
gether, like iron, without the afiiftance of
any other metal. After having heated two
pieces of platina to whitenefs, which had
been cuppelled in the furnace of Seves, he
placed them one on the other, and flriking
C c 2 then*

404 PLATINA.

them brifldy with the hammer, they welded
together as quickly and firmly as two pieces
of iron would have done* The great im-
portance of this experiment, with refpect to
the arts, need not be infifted on.

Macquer could not obtain an alloy with
forged iron and platina : this mixed metal
would poffefs the great advantage of uniting
the hardnefs of fteel with a eonfiderable
ductility, or at leaft it would not be brittle
like fteel. The Englifli chemift we have
quoted melted a mixture of caft iron and
platina; the alloy was fo hard as not to be
touched by the file ; it had a flight degree
of ductility, but broke fhort when ignited.
Platina communicates hardnefs to copper,
with which it melts with eonfiderable faci-
lity : this alloy is ductile, when the dofe of
copper is three or four times greater than
that of platina ; it is capable of taking the
moft beautiful polifli, and was not tar-
nifhed in the air during the fpace of ten
years.

Platina partly deftroys the ductility of fil-
ver, augments its hardnefs, and impairs its
colour. This mixture is very difficult to
fufe ; by fufion and reft the two metals
are feparated. Lewis obferved, that fil-
ver melted with platina was thrown up
againft the fides of a crucible, with a kind
of explofion ; a property which appears to
belong to filver alone ; for M. Darcet has ob-
ferved that this metal breaks balls of porce-
lain,

PLATINA. 405

fain, in which it is inclofed, and is thrown
out by the adtion of the fire.

Platina does not readily combine with
gold, but by the help of a very ftrong fire.
It greatly alters the colour of this metal,
unlefs its quantity be very fmall; thus, for ex-
ample, a forty-feventh part of platina, and all
the proportions below that, do not greatly
change the colour of gold. Platina does not
much impair the dudtility of gold, which is
iefs affedted than any other metal by the ad*
mixture. The fpccific gravity of platina be-
ing nearly equal to that of gold, might give
rife to frauds ; and for this reafon the Spa-
nish miniftry have prohibited its exportation :
however, fince chemiftry has difcovered me-
thods for diftinguifhing the alloy of gold
with platina, and even of platina alloyed
with gold, thefe fears ought no longer to be
attended to $ and it is much to be defired,
that platina may no longer be prohibited,
but that this new metal, which promifes
fuch confiderable advantages to fociety, may
become an article of commerce.

The folution of fal-ammoniac, as we have
obferyed, has the property of precipitating
platina; if, therefore, gold be fufpedted to
be alloyed with platina, its folution in aqua
regia may be aflayed with a folution of fal-
ammoniac. The fmall quantity of platina
it contains will occafion an orange, or red-
dim precipitate ; if no precipitate is thrown
C c 3 down,

406 PLATINA.

down, the gold does not contain platina. If
it fhould happen, that the valuable proper-
ties of platina fhould at fome future time
render it more fcarce and valuable than gold,
it will not be in the power of avarice to de-
ceive us in alloying it with gold ; fince a fo-
lution of martial vitriol, which has the pro-
perty of precipitating the folution of gold
without producing any change in that of
platina, would immediately expofe the de-
ception. A piece of tin, plunged in a folu-
tion of platina alloyed with gold, would
likewife fhew the prefence of the latter, by
becoming covered with a purple precipitate;
whereas platina gives only a dirty brown
precipitate, of a reddifh colour: this laft
precipitate likewife does not colour glafs,
whereas the precipitate of gold gives it a
purple colour.

All the properties of platina, which we
have examined, appear to prove that this
fubftance is a peculiar metal : its want of
dudlility and fufibility, which have been
confidered by fome writers as ftrong objec-
tions to this opinion, are not capable of
overthrowing it; fince there is perhaps a
lefs difference between the fufibility of pla-
tina and forged iron, than between that of
forged iron and lead, and fince its want
of duftility arifes from its not having un-
dergone complete fufion. As to the opi-
nion of thofe philofophers, who confider

platina.

PLATINA. 407

platina as a natural alloy of iron and of gold,
however ingenious and fatisfactory it may
appear, it is impoffible to admit it, until
the metal has been feparated into the two
others by an accurate analyfis, and until
platina can be better imitated by the arti-
ficial alloy of gold and iron. Laftly, Mac-
quer has made a very itrong objection againft
this laft opinion, by oblerving, that the
more platina is deprived of the iron it con-
tains, the greater is the difference between
its external appearances and.thofe of gold.

The important ufes to which this precious
metal may be applied, will be eafily con-
ceived, when it is confidered that it unites
the indeftruclibility of gold, to a degree of
hardnefs almoft equal to that of iron ; that it
refifts the action of the moft violent fire,
and alfo of the moil concentrated acids. It
cannot be doubted, but that chemiftry, and
the arts, would be in the higheft degree be-
nefited by its being applied to ufeful pur-
pofes.*

* Platina, when purified from iron by repeated coclion
in fpirit of fait, folution in aqua regia, and precipitation of
the iron by aqua regia, may be fufed with a ftrong heat.
It may then be rolled into thin plates, feems nearly as
malleable as foft iron, is fcarcely diftinguifhable from filver
on the touch- done, does not at all obey the magnet, and
has a fpecific gravity of nearly 23,000. T.

C c 4, CHAP.

408 BITUMENS,

CHAP. XXII.

GENUS VL
Concerning Bitumens in general.*

T^ITUMENS are combuftible, folid, foft,
■*-* or fluid fubftances, whofe fmell is
ftrong, acrid, or aromatic, and which ap-
pears to be much more compounded than
thofe bodies of tl\e mineral kingdom we have
hitherto examined. They are found either
in ftrata, in the internal part of the earth, or
exuding through the clefts of rocks, or float-
ing on thefurface of waters. Their character
is to burn moft commonly with a rapid
flame when heated with contact of air, like
thofe matters formed by the organs of vege-
tables and animals, and diftinguifhed by the
name of oils. Their analylis is much lefs
perfeft than that of earthy, faline, or me-
tallic matters ; becaufe the action of fire
greatly alters them, and developes principles
which re-act on each other, in proportion
as they are volatilized. In this refpect bi-
tumens refemble vegetable and animal fub-
ftances. By diftillation they afford water, or

* It is proper to remind the reader that we have divided
combuftible minerals into fix genera, viz. Diamond, in-
flammable gas, fulphur, plumbago, metals and bitumens* F.

an

BITUMENS. 409

an odorous phlegm, more or lefs coloured,
a faline acid fait, often concrete, fome-
times volatile alkali and oils, light towards
the beginning, and more thick and coloured
in proportion as the difiillation advances, and
the fire is more aftive. After this analyfis a
coal remains, which in the different fpecies
of bitumens is either denfe, light, brilliant,
or compaft. This analyfis fhews, that thefe
inflammable fubftances have a vegetable or
animal origin, as we (hall obferve more fully
after we have fpoken of their general pro-
perties.

Bitumens are fubjedl to fome alterations
from light. When fluid, their colour becomes
deeper, and their fmell is changed, if pre-
ferved in tranfparent veflels. The air thickens
them by the fucceflive evaporation of their
moifture, which is taken up fo much the
more readily as the air is drier. Their odo-
rous principle, or fpiritus redtor, is diflipated
in the fame manner, as they gradually pafs
from the ftate of fluidity to that of tenacity
and folidity. A great number of years how-
ever are neceflary to produce this laft alte-
ration.

Water, in which bitumens are boiled, does
not diflblve them, but it becomes charged
with their fpiritus reftor, and emits the
peculiar fmell of the bitumen. It feems,
therefore, that water has a ftronger affinity
with the odorant principle, than the oily

matter

4IO BITUMENS,

matter of the bitumen ; and that the whole
fmell of thefe fubftances might perhaps be
taken away in this manner.

The a&ion of the falino-terreftrial fub-
ftances on bitumens has not yet been exa-
mined ; lime, however, as well as pure
alkalis, feems capable of uniting with thefe
combuftible matters, and forming compounds
foluble in water, which are called foaps.

The manner in which the mineral acids
are capable of afting on bitumens, is not
known. It is probable, that they would
diffolve or burn them according to their flats
of concentration, as they do oils.

The adtion of neutral falts, of inflamma-r
ble gas, of fulphur, and of metals, on bi-
tumens, has not been examined ; and in
general the chemical properties of thefe fub-
ftances are but little known. This field of
experiment is intirely new, and certainly
promifes valuable and ufeful refults.

Natural hiftorians have paid a much greater
attention to the origin and formation of bi-
tumens, than chemifts have to their analyfis.
There have been many opinions refpeding
this fubjeft. Some have thought that thefe
combuftible fubftances properly belong tot
the mineral kingdom, and that they have
the fame relation to minerals, as oils and
refins have to organic fubftances. This
analogy, though ftriking to the imagination,
does not agree with the fa&s, for there is

BO

BITUMENS. 411

no fubftance in the mineral kingdom which
pofielfes the oily character. The opinion of
thofe therefore, who attribute the origin of
bitumens to vegetable fubftances buried in the
earth, and altered by the action of mineral acids,
has met with a much better reception. In
fact, every circumftance proves, that bitu-
mens are produced from organic fubftances.
A great number of bodies of this kind, whofe
form is ilill diftinguifhable, is conftantly
found in their vicinities; they have, beiides,
the chemical characters of fubftances formed
by the procefies of animation, and have been
imitated, in a certain degree, by combining
oils with the concentrated vitriolic acid.
We fhall fee in the chemical hiftory of ve-
getable fubftances, that oil of vitriol in con-
tact with effential oils, hardens and blackens
them, and communicates to them a ftrong
and penetrating fmell, refembling that of
bitumens. But can it be anerted that thefe
fubftances are in all cafes formed by vege-
table fubftances buried in the earth, as moft
naturalifts have affirmed, and that animal
fubftances have contributed nothing to their
formation ? The great quantity of bitumens
which exift in the external part of the earth,
compared with the fmall quantity of wood
and of trees found in their vicinity, and more
efpecially the fmall proportion of oily mat-
ter contained in vegetables, feem to contra-
dict that opinion which attributes the origin

of

412 BITUMENS.

of bitumens folely to produ&ions of the ve-
getable kingdom ; on the other hand, the
abundance of thefe combuftible bodies in
places where fcarcely any traces of vegeta-
bles are found, and the almoft conftant
exiftence of the exuviae of animals heaped
above bitumens, may induce us to believe,
that thefe organic beings have contributed
greatly, and perhaps even more than vege-
tables, to the formation of fome of the
kinds. We may likewife obferve, that the
fucceffive ft rata of certain bitumens which
are found in continued mafles in the internal
part of the globe, prove, that thefe fubftan-
ces have been depofited flowly, and by means,
of water ; and that their formation' corre-
fponds to the aera in which immenfe mafles
of fhells, or other marine fubftances, have
been formed by the fea. They have, there-
fore, been in a fluid ftate, and are become hard
by the lapfe of time and the unremitted adtion
of faline, or other agents, which the inte-
rior part of the earth contains in large quan-
tities. Such is the opinion which M. Par-
mentier, member of the College of Phar-
macy has exhibited, refpedting the origin
of pit-coal, in a memoir which he read at
the opening of the courfe ofledures before
that Society. The oils and fats of marine
animals appear, therefore, to be one of the
matters ufed by nature in the formation of
certain bitumens; while there are others,

whofe

AMBER. 413

whofe origin is manifeftly vegetable, and
arifes from the refins or effential oils, buried
and changed in the earth.

The number of bitumens is very confi-
derable. Naturalifts have divided them into
feveral genera. As we here confider them
chemically, we fhall divide them into fpe-
cies or kinds ; becaufe they have all, in
fadl, the fame characters relative to their
chemical properties ; fome are liquid, others
are of a foft confiftence, and others are folid,
among which laft fome are hard and fufcep-
tible of a polifh, while others are friable.
We are acquainted with fix fpecies, very
diftindt from each other, which may com-
prehend a great number of varieties. Thefe
fix fpecies, whofe hiftory we fhall proceed
to recite, are amber, afphaltos or bitumen
Judaicum, jet, pit-coal, ambergris, and pe-
troleum.

CHAP. XXIII.

SPECIES I.

Amber.

AMBER, the moft beautiful of all the
^^ bitumens, is found in irregular mafTes
of a yellow or brown colour, either tran-
fparent or opake, of a ftratified or fcaly

texture ;

4T4 AMBEit*

texture ; it takes a very good polifh ; after
a flight rubbing it becomes elec\ric, and at-
tracts ftraws and fmall bodies. The ancients,
who were acquainted with this property,
gave amber the name of elecTxum, whence
the modern term electricity is derived.

This bitumen is of a confiderable hard-
nefs, approaching to that of certain ftones,
which induces Hartman, a naturalift who
lived towards the conclufion of the laft cen-
tury, to rank it among precious ftones, though
it is friable and brittle. When pulverized it
emits an agreeable fmell. Infects, in a fine
ftate of prefervation, are often found within
it, which proves that it has been liquid, and
in that ftate has enveloped thofe fmall bodies.
Amber is ufually dug out of the earth at
various depths ; it is found under coloured
fands in fmall incoherent mafles, and dif-
perfed on ftrata of pyritaceous earth : above
it wood is ufually found, charged with black-
ifh bituminous matter ; whence it has been
concluded, that it is formed by a refinous
fubftance altered by the vitriolic acid of py-
rites. It likewife is found floating on the
banks of the fea ; as for example, on the
fhores of the Baltic in Ducal Pruflia. The
mountains of Provence near the town of
Sifteron, the Marquifate of Ancona and the
Duchy of Spoletto in Italy, Sicily, Poland,
Sweden, and many other countries likewife
afford it. The colour, texture, tranfparency,

or

AMBER. 415

or opacity of this bitumen, have caufed it to
be diflinguifhed into a confiderable number
of varieties, which, after Wallerius, we may
reduce to the following :
Varieties.

1. White tranfparent amber.

2. Pale yellow tranfparent amber.

3. Orange yellow tranfparent amber.

4. Golden yellow tranfparent amber, chry-

felectrum of the ancients.

5. Deep red tranfparent amber.

6. Opake white amber, leucelectrum.

7. Opake yellow amber.

8. Opake brown amber.

9. Amber, coloured green or blue by fo-

reign fubflances.
10. Veined or clouded amber.
It may likewife be diflinguifhed into a great
number of varieties, according to the acci-
dental circumftances its internal parts pre-
fent -, but it is neceffary to obferve, with
refpecl: to the price of the fpecimens of amber
remarkable for their magnitude, their tran-
fparency, or the well preferved infecls con-
tained within them, that it is poffible to be.
deceived in this refpecl:, fince many perfons
poffefs the art of giving it tranfparency or
colour at pleafure, and of foftening it fuffi-
cient to introduce foreign bodies. Walle-
rius affirms, that the gold-coloured amber
never owes its tranfparency to art, but that

which

4l6 AMBER,

which art has rendered tranfparent, is always
of a pale colour.

Though it is probable that this bitumen
owes its origin to refinous vegetable matters,
many naturalifts have entertained different
opinions refpedting its formation ; fome have
confidered it as the indurated urine of certain
quadrupeds ; others as a bitumen detached
from the earth by the fea, which is become
hard and dry by the aftion of the fun's rays.
This clafs of naturalifts confider it as a pe-
culiar mineral juice ; fuch was the opinion
of an ancient naturalift named Philemon,
and quoted by Pliny. George Agricola re-
vived this opinion ; Frederic Hoffman fup-
pofed it to be formed out of a light oil, Se-
parated from bituminous woods by heat, and
thickened by the vitriolic acid. This opinion
of Hoffman cannot, however, be admitted,
becaufe it is not conceivable how an oil fepa-
rated in the bowels of the earth, can inclofe
and contain animals which live only at its fur*
face. It has hitherto been thought, that amber
is a refinous juice which flows from fome tree;
that this juice, buried more or lefs deeply in
the earth, by the convulfions the globe has
experienced, becomes hardened by impregna-
tion with the mineral and faline vapours
which circulate within the earth. It is not
probable that it has been altered by concen-
trated acids ; for experience teaches us, that
the aftion of thefe acids would have blacken-
ed

AMBER. 417

fed it, and converted it into the ftate of coal.
Pliny thinks that amber is nothing but the
refin of the pine, hardened by cold. M.
Girtanner thinks, that it is a vegetable oil
rendered concrete by the acid of ants ; it is
that fpecies of ants called formica rufa by
Linnseus, which prepares it, according to
this author. Theie infedts dwell in old fo-
refts of fir trees, where the foffil amber is
found, which is ductile like wax, and be-
comes hard by expofure to air.

Amber, expofed to the fire, does not lique-
fy, but by a confiderable heat it foftens and
fwells very mqch ; when heated with con-
tact of air it takes fire, and emits a very thick
and odorous fume -y its flame is yellow -
ifh, variegated with green and blue; and af-
ter its combuflion it leaves a bright black
charcoal, which by incineration affords a
very fmall quantity of black brown earth.
Bourdelin, in his Memoir on Amber, (Acad.
1742) obtained but j8 grains of this earth
by burning two pounds of amber ; half a
pound of the fame bitumen burned and
calcined in a crucible, afforded him, in a
fecond operation, twelve grains of earthy
refidue, from which he extracted iron by
the magnet.

Amber diftilled in a retort by a heat gradu-
ally raifed, affords a phlegm of a red colour,
and manifeftly acid ; this acid fpirit retains
the ffrong fmell of amber : qxx acid volatile

Vol. III. D d fait

4l8 AMBER.

fait afterwards paries over, which cryftallizes
in fmall white, or yellowifli needles in the
neck of the retort. This fait is fucceeded by
a white and light oil of a very penetrating
fmell ; the oil by degrees becomes coloured
in proportion as the heat is raifed, and
towards the end is brown, blackifh, thick,
and vifcid, like the empyreumatic oils : while
thefe two oils pafs, a certain quantity of vo-
latile fait, more and more coloured, is fub-
limed. The refidue after this operation is a
black mafs of the figure of the bottom of the
veffel, brittle, and refembling bitumen Ju-
daicum. George Agricola made the fame
obfervation near three centuries ago, on
the refidue of diftilled amber. If the opera-
tion be managed by a gentle heat, cautioufly
conducted, and the quantity of amber be
confiderable, thefe products may all be ob-
tained feparately, by changing the receivers.
It is ufual however to receive them in the fame
veffel, and afterwards to rectify by a gentle
heat; the fpirit is partly difcoloured by
this rectification. The oil which becomes
black at the end of the operation, on ac-
count of the carbonaceous portion, and
becaufe the acid has acted on its principles,
may be rendered very clear and light, by
feveral fucceflive diflillations. Rouelle the
elder has defcribed a very good procefs for
obtaining it in this ftate by one operation :
for this purpofe the oil mull be put into a

glafs

AMEER. 419

glafs alembic with water, and diftilled by
the heat of boiling water ; the pu reft por-
tion, or the oily part which is volatile at this
degree of heat, on account of its levity, paffes
over with the water, above which it floats in
the receiver : if it be defigned to preferve it
in this ftate, it muft be kept in veffels of
ftone-ware ; for the rays of light which pais
through glafs veffels give it a yellow, and
even a browrn colour in procefs of time.

This analyfis fhews, that amber confifts
of a large quantity of oil rendered concrete by
an acid, and that it likewife contains a very
fmall quantity of earth, whofe nature has not
been yet examined, with a few particles of
iron.

The oil of amber appears to referable ef-
fential oils in volatility, fmell, and inflam-
mability : it feems capable of forming foaps
with alkalies.

The volatile fait of amber was for fome
time confidered as an alkaline fait. Glacer,
Lefevre, Charas, and Jean-Maurice Hoff-
man, profeffor at Altdorf, were of this opi-
nion. Barchufen, and Bolduc the elder, were
theflrft chemifts, who in the laft century ob-
ferved the acid nature of this fait. All fubfe-
quent chemifts have admitted this difcovery,
but they have not agreed concerning the
nature of the acid. Frederic Hoffman, from
the confideration that amber is found in Pruf-
fia among the ftrata of metals filled with py-
rites, imagined that this fait is formed from
D d 2 the

420 AMBER.

the vitriolic acid. Neumann appears to b&
of the fame opinion. Bourdelin, in thfc
Memoir we have quoted, relates feveral ex-
periments he made to determine the nature
of this fait : He firft obferves, that the fait
of amber obtained by diftillation, however
white and pure it may appear, always con-
tains an oily fubftance ; and it is doubtlefs
to this oily fubftance, that its fmell, and the
degree of combuftibility it exhibits when
thrown on burning coals, are owing : he
tried feveral methods of depriving it of this
fubftance. We (hall fee when we examine
the nature and properties of ardent fpirit*
that this fluid could not anfwer his purpofe^
neither was the fixed alkali alone which he
digefted on amber with the intention of de-
priving it of its fat and oily part, and of ob-
taining its fait feparate, attended with greater
fuccefs ; it only diffolved a fmall quantity of
the bitumen, and affumed a lixivial and faline
tafte, refembling that of fea fait. Laftly,
Bourdelin could not difcover a better procefs
for uniting the pure acid of amber, deprived
of oily matter, with fixed alkali, than to de-
tonate a mixture of two parts of nitre with
one part of the bitumen : he lixivkted the
refidue of this detonation with diftilled wa-
ter ; the lixivium was of an amber colour,
precipitating the folution of filver in white
fcales, and that of mercury of the fame co-
lour. Many other metallic folutions were

likewife

AMBER. 421

likewife decompofed by it, but Bourdelin
coniidered only the two firil as conclufive :
they appeared to him to (hew, that the acid
of amber was the fame as that of marine fait,
iince it prefented the fame phenomena as
this laft with the nitrous folutions of mer-
cury and lilver. The lixivium of the refidue
of the detonation of amber with nitre afford-
ed, by evaporation in the air, a mucilagi-
nous fubftance, in the middle of which
fquare long cryftals were depofited ; whofe
form, filine tafle, decrepitation on hot coals,
and more particularly the considerable effer-
vefcence and odour of marine acid, which
they emitted by the affufion of oil of vitriol,
convinced this author that fpirit of fait was
united with the bafe of nitre. Notwith-
standing this analyiis, which is very exact
for the time of Bourdelin, the chemifts who
examined the fait of amber fince his time,
did not find it analogous to the muriatic acid,
but difcovered in it all the characters of an
oily vegetable acid. Bergman, who appears
to have adopted this opinion, gives the fol-
lowing account of the elective affinities of
this fait. The acid of amber obtained by
fublimation, and purified by fuccefiive folu-
tions and cryftallizations, forms cryflalliza-
ble and deliquefcent neutral falts, wTith pot-
am and volatile alkali ; with foda it affords
a fait which does not attract the moifture of
-the air; with lime or barytes, it conftitutes
D d 3 falts,

422 AMBER.

falts of difficult folubility ; magnefia forms
with it a thick matter, refembling gum ; it
diflblves metallic calces ; and the falts pro-
duced by thefe folutions are for the mod part
cryftallizable and permanent.

Ponderous earth, lime, and magnefia, ac-
cording to him, take the acid of amber from
alkalies ; ponderous earth decompofes fucci-
nated lime and magnefia; and lime-water
precipitates the magnefia from this acid.

The examination of the chemical proper-
ties of this bitumen has not been carried
farther ; it is not even known in what man-
ner the other acids act upon it. Frederic
Hoffnjan affirms, that it may be totally dif-
folved in a lixivium of cauftic alkali, and in
the acid .of vitriol. It is known, that the
eflential oil of amber unites with the cauftic
volatile alkali, and forms by fimple mixture
and agitation a kind of liquid foap, of a milky
white, and very penetrating odour, known
in pharmacy by the name of Eau de luce ;
and laftly, that this fame oil diflblves ful-
phur by the affiftance of the heat of a water-
bath, and conftitutes a medicine called fuc-
cinated balfam of fulphur.

Amber is ufed in medicine as an antifpaf-
modic , it has been recommended in hyfteric
and hypochondriacal affections, the fuppref-
fion of the monthly courfes, the gonorrhoea,
fluor albus, &c. It is ufed in fubftance,

after

AMBER. 423

after having been warned with hot water,
and reduced into fine powder by levigation ;
it is ufed in ftrengthening and refolving fu-
migations, by throwing the powder of this
bitumen on a very hot brick, and directing
the fumes to the part propofed to be
acted on. The volatile fpirit and incifive
fait of amber are regarded as cordial and
antifeptic. The oil of amber is externally
and internally ufed for the fame purpofes as
amber itfelf, but is prefcribed in fmaller
dofes, on account of its greater activity.
The fuccinated balfam of fulphur, which is
given in the dofe of a few drops, in proper
fluids, or mixed with other fubftances to
form pills, is found fuccefsful in pituitous
affections or defluxions of the breaft, the
reins, &c. A fyrup, called fyrup of amber,
is made with fpirit of amber and opium, and
advantageoufly ufed as a fedative, anodyne,
and antifpafmodic remedy. Eau de luce,
which is prepared by pouring a few drops
of oil of amber into a bottleful of cauftic
volatile alkali, and agitating the mixture till
it becomes of a white milky colour, has
been long ufed as a powerful ftimulant in
fainting fits. It is held to the nofe, whofe
nerves it ftimulates, and by the fneezing
which it excites, the fluicjs are put in motion,
and the patient recovers.

The fined pieces of amber are cut and

turned into vales, heads of canes, necklaces,

D d 4 bracelets,

424 ASFHALTOS.

bracelets, fnuff-boxes, &c. Thefe kinds of
toys are no longer efteemed among us, lince
diamonds and jewellery are become more
known; but they are carried into Perfia,
China, and other nations, who (till efteem
them as great rarities. Wallerius affirms,
that the moft tranfparent pieces may be ufed
to make microfcopes, burning glaffes, prifms,
&c. It is affirmed, that the King of Pruffia
has a burning mirror of amber, of a foot in
diameter; and that there is a column of am-
ber, ten feet in heighth, and of a beautiful
luftre, in the cabinet of the Duke of Flo-
rence. Two pieces of this bitumen may be
fluck together, by fmearing them with oil
of tartar, and preffing them together hot.

CHAP. XXIV.
SPECIES II.

Afphaltos,

ASPHALTOS, or bitumen Judaicum, is
a black, ponderous, folid mining bitu-
men which breaks readily with a vitreous
fradhire. A thin piece of this bitumen ap-
pears red, when placed between the eye and
the light. Afphaltos has no fmell when it is
cold, but acquires a flight fmell by rubbing.
Jt is found on the waters of the lake Afphal-

tites*

ASPHALTOS. * 425

tites, or the Dead Sea, in Judea, near which
were the ancient towns of Sodom and Go-
morrah. The inhabitants, incommoded by the
fmell emitted by this bitumen on the fur-
face of the waters, and allured by the profit
they derive from it, are careful in collecting
it. Lemery, in his Dictionaire des Drogues,
affirms, that the afphaltos fweats out of the
earth, in the form of a liquid pitch ; and
rifing above the waters of the Dead Sea, is
condenfed by the heat of the fun, and the
action of the fait, which thofe waters contain
in large quantities. It is likewife found in
feveral lakes in China.

The afphaltos in commerce, is obtained,
according to Valmont de Bomare, from the
mines of Daunemore, and efpecially in the
principality of Neufchatel and Wallengin.
It is of two colours, according to this natu-
ralift, blackifh and greyifh or fawn-colour;
but this afphaltos is far from being pure,
and feems to be merely an earth, hardened
and penetrated by the bitumen.

Naturalifts are divided in their opinion
refpecting the origin of afphaltos, as well as
of all other kinds of bitumen : fome fuppofe
it to be a mineral product, formed by an
acid, united with a fat fubftance, in the
bowels of the earth -y others confider it as a
vegetable refinous fubftance buried, and al-
tered by the mineral acids. The mod gene-
rally received, and moil; probable opinion,

is,

426 ASPHALTOS.

is, that it has the fame origin as amber, and
is formed of this laft bitumen, changed by
the adtion of fubterraneous fires. This opi-
nion is founded on the circumftance, that
amber, melted and deprived of a part of its
fait by the adion of fire, becomes brittle,
and perfectly fimilar to afphaltos : but this
dodtrine cannot be folidly eftablifhed, but
by a comparative analyfis of this refidue
of amber, and of afphaltos ; and the latter
bitumen has not been yet examined with all
the accuracy which is neceflary to eftablifh
the analogy.

Afphaltos, expofed to heat, liquefies, fwells
up, and burns with aflame and thick fmoke,
whofe fmell is ftrong, acrid, and difagree-
able : by diftillation, it affords an oil of the
colour of brown petroleum, and an acid
phlegm.

Afphaltos is employed by the Arabians and
Indians for the fame purpofes as pitch, in
coating their vefTels, &c. It enters into the
compofition of the black varnifh of china,
and the artificial fires which burn on the
furface of water. The Egyptians ufed it to
embalm their dead; but it was not employ-
ed by the poor, who could not procure fuch
precious antifeptic fubftances. Wallerius
affirms, that a kind of afphaltos is prepared,
in commerce, with thickened pitch, or by
mixing and melting the latter with a certain
quantity of the true balfam of Judea ; but

this

JET. 427

this fraud may be difcovered by means of
fpirit of wine, which intirely diflblves the
pitch, and only takes a pale colour with af-
phaltos.

CHAP. XXV,
SPECIES III.

Jet-

JET, called by the Latins gagas, black
amber by Pliny, pangitis by Strabo, &c.
is a black bitumen, hard and compact, like
certain ftones ; brilliant and vitreous in its
fracture, and capable of taking a good polifh.
by friction : it attracts light fubftances, and
appears to be electric, like amber: it has no
fmell, but when heated, it acquires one nearly
refembling that of bitumen Judaicum.

Jet is found in France, in Provence, and
in the county of Foix ; there is likewife
a quarry where it is extracted at Beleftat,
in the Pyrenean mountains ; it is likewife
found in Sweden, Germany, and Ireland.
Jet is found difpofed in ftrata which contain
pyrites, in which it refembles the ftrata of
coal, and moft other fbitumens.

This bitumen foftens and melts ; when
ftrongly heated, it burns with a fetid odour;
by diftillation it affords an oil and an acid.

Among

428 PIT-COAL.

Among the different opinions refpecl-
ing the formation of jet, the moft pro-
bable, is that which fuppofes it to confift of
afphaltos, hardened by time : this opinion
has been adopted by the learned Wallerius.

Jet is ufed to make mourning toys. It
is wrought, at Wirtemburg, into bracelets,
buttons, boxes, &c.

CHAP. XXVI,
SPECIES IV.

Pit-Coal.

THE name of foffil-coal, pit-coal, ftone-
coal, lithantrax, &c. is given to a
black foliated bituminous matter, either of a
bright or dull appearance, which eafily
breaks, and has neither the confiftence nor
the purity of the bitumens before defcribed.
This bitumen has received the name it
bears, in confequence of its combuftible
property, and the ufes it is applied to in
many countries. It is found within the earth,
below ftony beds of various degrees of
hardnefs, and alluminous and pyritaceous
fhifti. The latter coflftantly bear the print
of feveral vegetables of the family of fern,
moft of which, acording to the obfer-
vation of Bernard de Juffieu, are exotic.

Pit-

PIT-COAL. 429

Pit-coal is found at varioas depths within
the earth ; it is difpofed in horizontal or in-
clined ftrata, the latter difpofition being the
moft ufual ; the beds, or ftrata of which it
is compofed, differ in thicknefs, confiftence,
colour, weight, &c. Beds of fhells, and
foffil madrepores, are often obferved above
the ftrata of this bitumen, which has induced
feveral moderns, particularly M. Parmentier,
to conclude that pit-coal has been formed
in the fea, by the depofition and alteration
of oily or fat marine fubftances. Moft natu-
ralifts conlider it as the product of a refidue
of woods buried in the earth, and altered
by acids.

The mines of foffil- coal are wrought in
the fame manner as other mines, by digging
fhafts and drifts, and detaching the pieces
of this bitumen by pick-axes. The miners
are often expofed to the danger of lofing
their lives by the elaftic fluids which are
difengaged. The kind of mephitis called
choak-damp extinguifhes their candles, and
appears to be the cretaceous acid ; a kind of
inflammable gas is likewife developed in
mines, which fometimes produces dangerous
explosions.

Foffil-coal is very abundant in nature ; it
is found in England, Scotland, Ireland,
Heinault, Liege, Sweden, Bohemia, Saxony,
Many provinces in France afford it in abun-
dance,

43° PIT-COAL."

dance, efpecially Burgundy, Lyons, Forez,
Auvergne, Normandy, &c.

Foflil-coal is diftinguifhed into ftone-cdal,
or earthen coal, according to its hardnefs
and friability ; but the manner in which it
burns, and the phenomena it prefents dur-
ing its combuftion, afford characters much
better adapted to diftinguifh the different
forts. Wallerius diftinguifhes three forts
under this point of view: i. The fcaly
coal, which remains black after its combuf-
tion. 2. The compact and laminated coal,
which after having been burned, affords a
fpongy matter, fimilar to fcorias. 3. Fi-
brous pit-coal, refembling wood, which is
reduced into afhes by combuftion.

This bitumen, heated in contact with the
air, burns more flowly and difficultly, in pro-
portion as it is more heavy and compact.
When once perfectly fet on fire, it emits a
ftrong and durable heat, and is long before
it is confumed ; it may even be extinguifhed,
and ufed feveral fucceffive times for new
combuftions. Its inflammable matter appears
to be very denfe, and as it were fixed by an-
other incombuftible fubftance, which pre-
vents its diflipation. It emits a peculiarly
ftrong fmell, which, however, is not at all
fulphureous. When the coal is very pure,
and does not contain pyrites, the combuftion
of this bitumen appears to refemble that of
organic fubftances, particularly in the cir-

cumftance

PIT-COAL. 43I

cumftance of its being capable of being in-
terrupted, and burned again. In fad:, the
moll volatile, oily, and moil combuftible
part of pit-coal, is diflipated and inflamed by
the firft adtion of the heat; and if the com-
buftion be extinguifhed when this princi-
ple is diflipated, the bitumen retains no more
than the moil fixed and leaft inflammable
part of its oil, reduced into a true coaly
itate, and combined with an earthy bale. By
a procefs of this nature the Englifh prepare
their coke, which is pit-coal, deprived of
its oily fluid by the action of fire. What
happens in this experiment is eafily fhewn, by
heating the bitumen in clofed vefTels, with
the proper apparatus for diftillation : an al-
kaline phlegm, concrete volatile alkali, and
an oil, which becomes of a deeper colour, and
more heavy, in proportion as the diftillation
advances, are obtained; at the fame time that
a great quantity of elaftic and inflammable
fluid is difengaged, which is fuppofed to be oil
in the vapourous ftate, but is in fad a peculiar
kind of inflammable gas : in the retort there
remains a fcorified carbonaceous matter, {till
capable of burning, which is the coke of the
Englifh. If the a&ion of fire on pure pit-
coal be attended to, it is feen that it furrers
an evident foftening, and appears to undergo
an imperfect fufion ; and as this ftate might
be prejudicial to the fufion of ores, it is ne-
ceffary to deprive the coal of this property :

the

432 PIT-COAL.

the principle on which the foftening de-
pends being taken away, namely, the oil
which it contains in great abundance, the
coal is reduced into a ftate analogous to that
of charcoal made with vegetables. We muft
not forget to obferve, that the volatile alkali,
abundantly furniihed by pit-coal, favours
the opinion we have urged refpe&ing its
animal origin, fince, as we have elfewhere
feen, the fubftances afforded by the animal
kingdom always afford this fait by dis-
tillation. This analyfis of coal is made in
the large way in many parts of England;
and the different produces of pit-coal are
collected in a peculiar diftillatory apparatus :
the oil is employed inftead of pitch, the vo-
latile alkali ferves the manufactories of fal-
ammoniac, and the refidue is an excellent
coke. M. Faujas de Saint Fond has tranf-
ported this ufeful art into France, and the
experiments he has made at the King's
Garden have fucceeded perfectly well.*

* Every principle ofjuftice and equity demands that
the name of Lord Dundonald fhould not be parted over
in filence when this art is fpoken of. It is this gentleman,
whoj having the fpirit to rifque his fortune on a rational
and highly beneficial project, has done more fervice to
his country, and mankind at large, than if he had dis-
covered an hundred gold mines. The coke and mineral
tar are of infinite utility in the arts ; but I do not know
•whether the volatile alkali of this procefs is cheaper than
that ufually obtained from bones, nor whether the oil is
applied to the commercial purpofes. T.

Pit-

pit-coal. 433

Pit-coal is Angularly ufeful in countries
where wood is fcarce : it is employed as fuel
without any of that danger attributed by cer-
tain perfons to its ufe; for the fulphureous
vapour, which has been faid to be fpread
abroad during its combuftion, is not to be
feared, fince the moft accurate analyfis has
proved, that when pit-coal is very pure, it
does not contain the fmalleft portion of ful-
phur. Hence we may perceive how falfe and
fallacious are the pretences of certain ignorant
perfons, who affirm that they are in pofTeffion
of proceffes to deprive this bitumen of its
fulphur. Another confederation which ought
to engage us, efpecially in France, to ufe
pit-coal, is, that the mine-works confum-
ing immenfe quantities of charcoal, there is
reafon to fear that wood will, at no very dif-
tant period of time, become fcarce ; and it is
more efpecially in thofe kinds of works that
pit-coal ought to be ufed, as it long has
been by the Englifh.

Purified pit-coal confifts of coal deprived
of its oil by the a&ion of fire ; this kind of
charcoal burns without fmoke, without be-
coming foft, and without emitting any ftrong
fmell : in a word, it is a true coke, and is
preferable as fuel to be burned in the apart-
ments of a dwelling houfe.

One of the greateft inconveniences of pit-
coal, befides the very abundant and thick
fmoke it emits, and which blackens furniture,

Vol. III. E e is,

434 AMBERGRIS.

is, that the very rapid and abundant current
of air it requires for its combuftion raifes
and volatilizes part of its afhes, which fix
themfelves to the furrounding bodies ; but
thefe two inconveniences may in a great
meafure be remedied by well-conftrudted
chimnies, fo that the current excited by the
combuftion may be intirely carried out of
doors, without any part of it returning into
the chamber.

The. utility which this combuftible fub-
ftance will be of in France, is much greater
with refpedt to the arts and manufactures of
every kind ; and by availing ourfelves of this
fuel, wood for building, and other purpofes,
will be rendered cheaper.

CHAP. XXVII.
SPECIES V.

Ambergris.

AMBERGRIS is a concrete fubftance,
of a foft and tenacious confiftence, like
wax, marked with black and yellow fpots, and
of an agreeable and ftrong fmell when heated,
or rubbed : it is in irregular maffes, fome-
times rounded, confifting of layers of dif-
ferent kinds, more or lefs thick, accordingly
as they are united in great numbers. Pieces

have

AMBERGRIS. 435

have been found weighing more than two
hundred pounds : this fubftance has mani-
feftly been liquid, and has enveloped many
foreign matters; fuch as the bones of the
cuttle fifh, and other marine animals.

Ambergris is found floating on the fea,
near the Molucca iflands, Madagafcar, Suma-
tra, on the coaft of Coromandel, Brazil,
America, China, and Japan. Many American
fifhermen affured Dr. Schwediawer, that
they often found this fubftance, either among
the excrements of the fpecies of whale, called
by Linnasus phyfeter macrocephalus, or in
its ftomach, or in a veffel fituated in that
region.

Naturalifts diftinguifh many varieties of
ambergris : Wallerius admits, the fix fol-
lowing.

Varieties.

i. Ambergris fpotted with yellow.

2. fpotted with black. Thefe

two varieties are the moft valuable.

3. Ambergris of an uniform white.

4. of an uniform yellow.

j. ■■ — of an uniform brown.
6. of an uniform black.

It mud be obferved, that thefe varieties
depend on the mixture of certain marine
fubftances.

The learned have been greatly divided in

their opinion refpefting the origin of am-

E e 2 bergris.

436 AMBERGRIS,

bergris. Some confider it as a kind of pe*
troleum, iffuing out of the rocks, thickened
by the aftion of the fun, and of the falt-
v/ater : others have fuppofed it to be the
excrements of birds, which feed on odorous
plants; others again have attributed its origin
to the excrement of the fea-cow, or of the
crocodile, &c. Pommet and Lemery fup-
pofed it to be a mixture of wax and honey,
altered by the fun and the fea- water. M.
Formey, who adopted this opinion, has fup-
ported it by an experiment, which confifts
in digefting a mixture of wax and honey ;
he affirms, that a fweet fmell, very much
refembling that of amber, is emitted by
the produdt. Some Englifh writers have
confidered ambergris as an animal juice, de-
pofited in veffels placed near the origin of
the genital parts of the male whale 5 and
others have fuppofed it to be formed in the
urinary bladder of that creature : but both
thefe opinions are overthrown by the beaks
of the cuttle fifh, found in this concrete
matter. Laftly, M. Schwediawer, aftef ex-
amining a great number of fpecimens of am-
bergris, and inquiring into the reports of
feveral navigators, thinks that this fubftance
is formed in the alimentary canal of the
phyfeter macrocephalus, or fpecies of whale
from which fpermaceti is obtained. He con-
fiders ambergris as the excrement of this
creature, mixed with certain parts of its

nouriihment.

AMBERGRIS. 437

nourishment, i . Becaufe the fifhermen found
it in that whale. 2. Becaufe 'ambergris is
common in thofe regions which abound with
this fifh. 3. Becaufe the beak of the fepia
odtopedra, on which this animal feeds, are
always contained in it. 4, and laftly, Be-
caufe he has obferved that the black fpots
of this concrete fubftance are the feet of that
polypus. His inquiries have rendered this
opinion of the Japanefe, and of Kempfer,
the moft probable ; and nothing is now
wanting for its intire confirmation, but the
obfervation of fome real naturalifl, made on
the fpot.

Neverthelefs, this fubftance, analyzed by
Geoffroy, Neumann, Grim, and Brown, af-
forded the fame principles as bitumens; that
is to fay, an acid fpirit, a concrete acid fait,
oil, and a carbonaceous refidue, which induced
them to rank it among thofe bodies. But
M. Schwediawer obferves very truly, that the
calculi of animals afford an acid, and that the
prefence of this fait is a proof in favour of
his opinion, lince fats contain it in confider-
able quantities.

Ambergris is ftomachic, cordial, and an-
tifpafmodic. It is ufed in the dofe of a few
grains, in proper liquids, or mixed with
other fubftances, in the form of pills. The
odorous principle of this medicine is often too
ftrong and penetrating, fo as to be produc-
tive of noxious effedts. It is well known, that
E e 3 many

438 AMBERGRIS.

many perfons cannot endure its fmell, with-?
out experiencing all the difagreeable fymp-
toms which arife from nervous irritation :
it ought not therefore to be adminiftered
but with precaution. It has likewife been
regarded as a powerful aphrodifiac : fome
modern phyficians, however, think that
ambergris may be prefcribed in large dofes,
without producing any confiderable effedts.

The principal ufe of ambergris is to afford
a perfume for the toilet. It is ufually mixed
with muJk, which divides and attenuates its
fmell in fuch a manner as to render it more
fupportable ; but even in this ftate there are
many who diflike it.

As ambergris is an expenlive fubftance, it
is often adulterated, and mixed with various
other matters . True ambergris has the follow-
ing characters : it is flaky, of a fweet fmell,
and infipid; it melts without affording either
bubbles or fcum, when expofed to the flame
of a taper in a filver fpoon ; it floats upon
water, and does not adhere to a hot iron.
Ambergris, which does not poffefs all thefe
properties, is impure and adulterated.

C H A P.

PETROLEUM. 439

CHAP. XXVIII.
SPECIES VI.

Petroleum.

npHE name of petroleum is given to a
■* liquid, bituminous fubftance, which
flows between ftones or rocks, or in diffe-
rent places at the furface of the earth. This
oil differs in lightnefs, fmell, confiftence,
and inflammability, in its feveral fpecimens.
Authors have diftinguifhed a confiderable
number of varieties : they have given the
name of naphta to the lighteft, mofl trans-
parent, and mofl: inflammable petroleum ;
the name of petroleum, properly taken, is
applied to a liquid bitumen, rather thick,
and of a deep brown colour; and laftly, that
of mineral pitch is ufed to denote a black
thick bitumen, fcarcely liquid, but tenaci-
ous, and flicking to the fingers. The fol-
lowing varieties are defcribed by Wallerius,
and many other naturalifts.

Varieties.

i. White naphta.

2. Red naphta.

3. Green, or dark-coloured naphta.

4. Petroleum, mixed with earth.

E e 4 5, Petro-

440. PETROLEUM.

5. Petroleum exfuding from between
ftones.

6. Petroleum floating on the furface of
waters.

7. Mineral pitch or Malta.

8. Piffafphaltum. It is of a middle con-*
fiftence, between that of common petroleum
and afphaltos, or bitumen Judaicum.

The different naphtas are found in Italy,
in the duchy of Modena, and at Mount
Crocairo, twelve leagues from Plaifance.
Kempfer reports, in his Amoenitites Exotica,
that it is collected in large quantities in fe^
veral parts of Perfia. Petroleum is found in
Sicily, and many other parts of Italy ; in
France, and the village of Gabian in Lan-
guedcc; in Alia; at Neufchatel in Switzer-
land -, in Scotland, &c. The piiafphaltum
and mineral pitch were formerly brought
from Babylon, where it was ufed in the con-
ftrudtion of edifices; from Ragufa in Greece,
and the Tank or pond of Samofet, capital
of Comagena in Syria. It is at prefent ob-
tained from the principality of Neufchatel
and Wallengin ; from the Well de la Pege,
one league from Clermont-Ferrand in Au-
vergne ; and feveral other places. It muft
be obferved, with refpeft to the different
varieties we have pointed out, that they all
appear to have the fame origin, and differ
from each other only in fome particular mo-
dification. Moil naturalifts and chemifts

attribute

PETROLEUM. 44I

attribute the formation of petroleum to the
decompofition of folid bitumens by the ac-
tion of fubterraneous fires. They obferve that
naphta appears to be the lighted oil, which
is firft difengaged by the fire; and that
which fucceeds it, acquiring colour and
confidence, forms the different kinds of pe-
troleum : that, laftly, thefe united to earthy
fubftances, are altered by acids, and affume
the characters of mineral pitch, or pifiaf-
phaltum. In fupport of thefe opinions, they
have made a very accurate comparifon be-
tween thefe phenomena, and thole which the
diftillation of amber prefents, which in fadt
affords a kind of naphta, a petroleum more
or lefs brown, according to the degree of
heat, and time of the operation. And laftly,
they obferve that nature often prefents in
the fame place other kinds of petroleum,
from naphta, the lighted:, down to the mi-
neral pitch: fuch are the fluid bitumens ob-
tained from Mount Feftin, in the duchy of
Modena. Though this opinion is very pro-
bable, fome authors think that petroleum is
a mineral, oily combination, formed by the
vitriolic acid and fome fat fubftance ; but
this combination likewife would owe its
origin to certain organic fubftances, fince
fat matters are always formed by fuch.

The chemical properties of petroleum
have not yet been examined. Naphta is fo
volatile and combuftible, that it takes fire

on

442 PETROLEUM.

on the approach of any burning fubftance,
and feems even to attradt flame, on account
of its volatility : the brown petroleum af-
fords an acid phlegm, an oil, which at firft
refembles naphta, and becomes more denfe
and coloured, in proportion as the diftilla-
tion advances : a thick fubftance, refembling
pifafphaltum, remains in the retort, which
may be rendered dry and brittle, like af-
phaltos, and by a ftronger fire is reduced
intirely to the carbonaceous ftate. Alkalies
have fcarcely any aftion on petroleum ; the
vitriolic acid colours, and renders it thick ;
the nitrous acid inflames it, like effential
oils ; it readily diffolves fulphur, becomes
coloured by metallic calces, and unites, by
the affiftance of heat, to amber, which it
partly foftens, and partly diffolves.

The different fpecies of petroleum are ufed
for various purpofes in the countries where
they are obtained. Kempfer informs us that
they are ufed in Perfia for the purpofe of
illumination, and burned in lamps with a
wick ; they may likewife be ufed as fuel.
Lehman affirms, that naphta is for this pur-
pofe poured on a few handfuls of earth, and
afterwards lighted with paper : it immedi-
ately catches fire, and burns brifkly ; but at
the fame time emits a thick fmoke, which
flicks to the furrounding bodies, and has a
very difagreeable fmell : it has been thought
that petroleum enters into the compofitipa

of

MINERAL WATERS. 443

of the Greek fire ; the thicker kind is like-
wife ufed as mortar for building, for which
purpofe it is very folid and durable. By
decodtion of pifafphaltos with water, an oil
is obtained, which is ufed inftead of tar for
veffels.

Laftly, fome phyficians ufe petroleum
fuccefsfully in paralytic weakneffes, and dif-
orders of the mufcles, applying it externally
to the fkin, or expofing the difeafed part to
its fmoke. Van Helmont afferts, that fric-
tions with petroleum are an excellent re-
medy for frozen limbs, and recommends it
as a good prefervative againft the impreffion
of cold.

SUPPLEMENT

TO THE ACCOUNT OF THE

MINERAL KINGDOM.

Concerning Mineral Waters, and the Me-
thods of analyzing them.

fN the former part of this work we have
* treated of all the fubflances in the mi-
neral kingdom, and have explained their
phyfical properties ; we fhall conclude the

hiftory

444 ANALYSIS OP

hiftory of this kingdom, by treating of mi-
neral waters, becaufe thefe fluids often hold
in folution earthy, faline, and metallic fub-
ftances, either together or feparate. It would
have been impofiible to have treated with
perfpicuity and order, refpefting them, with-
out firft explaining the properties of thofe
fubftances. Our examination of mineral
waters will therefore be more advantageoufly
placed here, as it may ferve inftead of a re-
capitulation of the general principles of the
chemical analyfis applied to minerals.

§ I. Definition and Hiftory of Mineral
Waters.

Waters, which contain minerals in folu-
tion, are diftinguifhed by the appellation
of mineral waters. But, as there is no
water found in nature, even among thofe
ufually reckoned the pureft, which is not
impregnated by fome of thefe fubftances,
the name of mineral waters ought to be con-
fined to fuch as are fufficiently impregnated
to produce a fenfible effeft on the animal
economy, fo as to cure or prevent the dis-
orders to which we are liable. * For this

reafon,

* It muft be obferved, that waters which do not contain
the principles in fufficient quantity to be rendered fenfible
by analyfis, may neverthelefs produce ftrong effects on the
animal economy, nothing more being necelTary than that

thejr

MINERAL WATERS. 445

reafon, the name of medicinal waters feems
to be much more applicable to thefe fluids
than that by which they are commonly
known, and which is too ftrongly efta-
blifhed to be changed.

The firft knowledge of mineral waters,
like every other branch of knowledge we
poffefs, was accidentally difcovered. The
good effects they produced on fuch as ufed
them, have doubtlefs been the caufe of dif-
tinguifhing them from common waters. The
firft philofophers who confidered their pro-
perties, attended only to their fenfible quali-
ties, fuch as colour, weight, or lightnefs,
imell, and tafte. Pliny, however, diftin-
guifhed a great number of waters, either by
their phyfical properties, or their ufes ; but
the inquiry after methods of afcertaining, by
medical proceffes, the quantity and quality
of the principles held in folution by mineral
waters, was not attempted till the feventeenth
century. Boyle is one of the firft who, in
the valuable experiments on colours, pub-
lifhed by him at Oxford in 1663, mentioned
feveral re-agents capable of indicating the
fubftances diflblved in water, by the altera-
tion produced in their colours. The aca-

they fhould be very light, briik, and their temperature
above that of common waters : the waters of Plombieres
and Luxeuil ac~r. in this manner ; and differ from the pure
water of other fprings only in their being of a hotter tem-
perature. Note of the Author.

demy

446 ANALYSIS OP

demy of fciences, from its firft inftitution,
was aware of the importance of analyzing
mineral waters; and Duclos, in 1667, at-
tempted the examination of the mineral wa-
ters of France : the refearches of this che<-
mift may be found in the original Memoirs
of this fociety. Boyle was particularly em*-
ployed in inquiries refpe.&ing mineral waters
about the end of the feventeenth century,
and published a treatife on this fubjedt in
1685. Boulduc, in the year 1729, published
a method, of analyzing waters, which is
much more perfect than any which were
employed before his time : it confifts in eva-
porating thefe fluids, at different times, and
feparating, by filtration, the fubftances which
are depofited, in proportion as the evapora-
tion proceeds.

Many celebrated chemifls have fince made
fuccefsful experiments on mineral waters,
and almoft every one made valuable difco-
veries refpe&ing the different principles con-
tained in thefe fluids. Boulduc difcovered na-
trum, and determined its properties; Le Roi,
phyfician of Montpellier, difcovered calca-
reous muriate ; Margraaf the muriate of
magnefia ; Prieftley cretaceous acid ; and
Monnet and Bergman the hepatic gas. The
two laft-mentioned chemifls, befides the dif-
coveries with which they have enriched the
art of analyzing waters, have publifhed com-
plete treatifes on the method of proceeding

in

MINERAL WATERS. 447

in this analyfis ; and have carried this part
of chemiftry to a degree of perfection and
accuracy, far exceeding that which it pof-
feffed before the time of their labours. We
are likewife in poifeffion of particular ana-
lyfes, made by very good chemifts, of a great
number of mineral waters, and which ferve
to throw great light on this inquiry, which,
with juftice, is efteemed one of the moft dif-
ficult in the whole art of chemiftry. The
limits we have prefcribed to ourfelves do not
permit us to enter at large into the hiftory
of the analyfis of waters, which may be
found in many treatifes ; but we fhall not
fail to mention the authors of difcoveries as
occaiion may require.

§ II. Principles contained in Mineral Waters.

It is but a few years fince the fubflances
capable of remaining in folution in water
have been accurately known. This appears
to have arifen from the want of accurate
chemical methods of afcertaining the nature
of thefe fubflances ; and the certainty of
their exiflence has naturally followed the
difcovery of methods of afcertaining them.
Another caufe which has retarded the pro-
grefs of fcience in this refpecl, is, that mine-
ral matters, diflblved in waters, are almofl
always in very fmall dofes, and are alio
mixed together in confiderable numbers, fo
that they mutually tend to conceal or alter

thofe

44^ ANALYSIS OF

thofe properties in which their diftin&ive
characters confifl. Neverthelefs, the nume-
rous experiments of the chemifts we have
quoted, and a great number of others, which
we fhall occafionally mention, have fhewn,
that fome mineral fubftances are often found
in waters, others fcarcely ever met with ;
and laftly, many which are never held in fo-
lution by that fluid. We fhall here confider
each clafs of thefe fubftances in order.

Quartzofe earth is fometimes fufpended in
waters ; and as it is in a ftate of extreme di-
vifion, it remains fufpended without preci-
pitating; but its quantity is extremely mi-
nute.

Clay likewife appears to exift in water:
the extreme fubtlety of this earth, by which
it is difperfed through the whole mafs of
water, caufes it to render them turbid. Ar-
gillaceous waters are whitifh, and have a
pearl, or opal colour ; they are likewife
fmooth, or greafy to the touch, and have
been called faponaccous waters.

Lime, magnefia, and ponderous earth, are
never found pure in waters ; they are always
combined with acids.

Fixed alkalies are never met with in a
ftate of purity in waters, but frequently
combined with acids, in the form of neutral
falts : the fame obfervation applies to the
volatile alkali, and molt acids, except the
cretaceous acid, which is often free, and in
pofleffion of all its properties in waters. It

conftitutes

MINERAL WATERS. 449

conflitutes a peculiar clafs of mineral waters,
known by the name of gafeous, fpirituous,
or acidulous waters.

Among the perfect neutral falts, fcarcely
any are met with but vitriol of foda or
Glauber's fait, the muriates of foda, and of
pot-afh, and cretaceous foda, which are fre-
quently diflblved in mineral waters; nitre,
and cretaceous tartar, are rarely found.

Selenite, calcareous muriate, chalk, Ep-
fom fait, or vitriol of magnefia, muriate of
magnefia, and cretaceous magnefia, are the
earthy falts which are moll commonly found
in waters. As to the calcareous nitre, and
nitre of magnefia, which fome chemifts have
aflerted they have met with, thefe falts are
fcarcely ever found in mineral waters, proper-
ly fo called, though they exiit in fait waters.

The argillaceous neutral falts, and falts
with bafe of ponderous earth, are fcarcely
ever diffblved in waters. Alum appears to
exift in fome waters.*

Pure inflammable gas has not yet been
found difTolved in mineral waters.

Pure fulphur has not been found in thefe

* We do not here mention the opinion of le Givre, and
other chemifts, who confider alum as one of the molt ufual
principles found in mineral waters. But accurate experi-
ments, made by M. Mitouart, have fhewn, that the wa-
ters of la Dominique de Vals contain alum ; and M.
Opoix has afcertained the exiftence of this fait in the water*
of Provins.-^Note of the Author.

Vol. III. F f fluids,

450 THE ANALYSIS

fluids, though it may exift very rarely, in
fmall quantities, in the ftate of liver of ful-
phur. Sulphureous waters are moft com-
monly mineralized by the hepatic gas, or
vapour of liver of fulphur.

Laftly, among metals, iron is moft com-
monly diflblved in waters, and may be found
in two ftates ; either combined with the cre-
taceous acid, or with the vitriolic acid. Some
chemifts have fuppofed that it was likewife
diflblved in its metallic ftate, without an acid
intermedium ; but as this metal fcarcely ever
exifts in nature, without being either in the
ftate of ruft, or of that of vitriol, the opi-
nion of thefe philofophers could only be
maintained at the time when the cretaceous
acid was not yet difcovered; and the folu-
bility of iron in water, without the afliftance
of the vitriolic acid, could not otherwife be
accounted for. Bergman affirms, that iron,
as well as manganefe, is found in certain
waters, combined with the muriatic acid.

Arfenic, and the vitriols of copper and
zink, which exift in many waters, commu-
nicate poifonous properties to them, and
fhew, when difcovered by analyfis, that the
ufe of fuch waters muft be carefully avoided.

Moft chemifts, at prefent, deny the ex-
iftence of bitumen in waters : in fad:, the
bitter tafte was the caufe why waters were
formerly fuppofed to contain thefe oily fub-
ftances / but it is now known that this tafte,

which

MINERAL WATERS. 451

which does not exift in bitumen, is produced
by the calcareous muriate.

There is no difficulty in conceiving how
water, which percolates through the interior
parts of the globe, and efpecially through the
mountains, may become charged with the dif-
ferent fubftances we have enumerated. It is
likewife clear, that, according to the nature
and extent of the ftrata of earth, through
which they pafs, mineral waters will be
more or lefs charged with thefe principles,
and that the quantity and nature of thefe
principles muft be fubjedt to great variations.

§ HI. The different Claffes of Mineral Waters.

It appears from what we have already ob-
ferved refpedting mineral waters, that thefe
fluids may be claffed according to the earthy,
faline, and metallic fubftances they hold in
folution ; and that the number of claffes, on
this principle, would be very confiderable :
but it muft be obferved, that none of thefe
fubftances are found fingle and alone in wa-
ters ; but on the contrary they are often dif-
folved, in the number of three, foui, five,
or even more. This circumftance creates a
difficulty in the methodical claiiification of
waters, relative to the principles that they
contain. However, if we attend to thofe fub-
ftances which are the moft abundantly con-
tained in waters, or whofe properties are
F f 2 the

452 THE ANALYSIS OF

the moft prevalent, we fhall be able to make
a diftindtion, which, though not very accu-
rate, will be fufficient to arrange thefe fluids,
and to form a judgment of their virtues.
Chemifts, who have attended to mineral wa-
ters in general, have availed themfelves of
this method. M. Monnet has eftablifhed
three claffes of mineral waters ; the alkaline,
the fulphureous, and the ferruginous : and
fubfequent difcoveries have enlarged the
number of claffes. M. Duchanoy, who has
publifhed a valuable treatife on the art of imi-
tating mineral waters, diftinguifhes ten, viz.
the gafeous, the alkaline, the earthy, the
ferruginous, the limple hot, the gafeous ther-
mal, the faponaceous, the fulphureous, the
bituminous, and the faline waters. Although
It may be urged as a reproach, that this au-
thor has made his claffes too numerous, fince
the pure gafeous and bituminous waters are
unknown ; yet his divifion is doubtlefs the
moft complete, and gives the moft accurate
idea of the nature of the different mineral
waters, and confequently is the beft fuited
to his fubjeft. We fhall here propofe a di-
vifion lefs extenfive, and in our opinion
more methodical, than that of M. Ducha-
noy; at the fame time obferving, that we
do not confider fimple thermal waters as
mineral waters, becaufe they confift merely
of heated water, according to the heft che-
mifts 5 and that we fhall not fpeak of bitu-
minous

MINERAL WATERS. 453

minous waters, becaufe none fuch have been
yet found.

All mineral waters may be arranged in
four clafles, viz. acidulous, faline, fulphu-
reous, and ferruginous waters.

Class I. Acidulous Waters.

Gafeous waters, which may with more
propriety be called acidulous waters, are
thofe in which the cretaceous acid predomi-
nates ; they are known by their fharp tafte,
and the facility with which they boil, and
afford bubbles by fimple agitation : they
redden the tincture of turnfole, precipitate
lime-water and liver of fulphur. As no wa-
ters have yet been difcovered which contain
this acid pure and alone, we think this clafs
may be divided into feveral orders, according
to the other principles contained in them, or
the modifications they exhibit. They all ap-
pear to contain more or lefs alkali and cal-
careous earth ; but their different degrees of
heat afford a good criterion for dividing
them into two orders ; the firft might com-
prehend cold, acidulous, and alkaline wa-
ters, fuch as thofe of Seltzer, Saint-Myon,
Bard, Langeac, Chateldon, Vals, &c. ; in
the fecond might be placed, hot, or ther-
mal, acidulous., and alkaline waters, as thofe
of Mount D'or, Vichy, Chatelgyon, &c.

F f 7 Class II.

454 THE ANALYSIS OF

Class II, Saline or Salt Waters.

By the name of faline waters, we under-
ftand with M. Duchanoy, fuch as contain
a fufficient quantity of neutral fait to aft
ftrongly on the animal economy, fo as moft
commonly to purge. The theory and nature
of thefe falts are eafily difcovered; they per-
fectly refemble the folutions of falts made
in our laboratories ; but they almoft always
contain two or three different fpecies of
falts. The vitriol of foda, or Glauber's fait,
is very rare ; vitriol of magnefia, or Epfom
fait, marine fait, or muriate of foda, calca-
reous and magnefian muriates, are the faline
principles which mineralize them, either
together or feparate. The waters of Sedlitz,
of Seydfchutz, and of Egra, abound with
Epfom fait, frequently mixed with muriate
of magnefia. Thofe of Balaruc contain ma-
rine fait, chalk, and the calcareous and mag-
nefian muriates; thofe of Bourbonne marine
fait, felenite, chalk ; and thofe of la Mothe
contain marine fait, felenite, chalk, Epfom
fait, muriate of magnefia, and an extractive
matter. It muft be here obferved, that falts
with bafe of magnelia, are much more com-
mon in waters than has hitherto been fup-
pofed ; and that few analyfes have yet been
made, ifl which they have been well diftiji-
guifhed from calcareous muriate.

Class

MINERAL WATERS, 455

Class III. Sulphureous Waters.-

The name of fulphureous waters has been
given to fuch mineral waters as appear to
poffefs fome of the properties of fulphur ;
fuch as the fmell, and the property of dif-
colouring filver. Chemifts have long been
ignorant of the true mineralizer of thefe
waters ; mod have fuppofed it to be ful-
phur, but they never fucceeded in exhibit-
ing it, or at leaft have found it in quantities
fcarcely perceptible. Thofe who have made
experiments on fome of thefe waters, have
allowed them to contain either fulphureous
fpirit or liver of fulphur. MefT. Venel and
Monnet, are the firft who oppofed this opi-
nion ; the latter in particular, nearly difco-
vered the truth, when he confidered fulphu-
reous waters as impregnated merely by the
vapour of liver of fulphur. Rouelle the
younger likewife affirmed, that thefe fluids
might be imitated by agitating water in con-
tact with air, difengaged from liver of ful-
phur by an acid. Bergman carried this
doctrine much farther, by examining the
properties of hepatic gas, which we have
fpoken of under the article fulphur : he has
proved that this gas mineralizes fulphure-
ous waters, which he therefore calls he-
patic waters, and has directed methods of
afcertaining the prefence of fulphur. Not-
F f 4 withftanding

456 THE ANALYSIS OF

withftanding thefe difcoveries, M. Ducha-
noy, fpeaking of fulphureous waters, admits
liver of fulphur, fometimes alkaline, fome-
times calcareous, or argillaceous. He fel-
lows the opinion of Le Roy of Montpellier;
who, as wre have obferved in the hiftory of
fulphur, propofed a liver of fulphur with
bafe of magnefia in imitating thefe waters.
It appears in fadl to be true, that there are
waters which contain a fmall quantity of
liver of fulphur ; while there are others,
which are mineralized only by hepatic gas.
In this cafe it will be necefiary to diftinguifli
fulphureous waters into two orders ; the
name of hepatic might, perhaps, be given
v/ith propriety to fuch as hold a fmall quan-
tity of liver of fulphur in folution, and he-
patized to fuch as are impregnated only with
the hepatic gas. The waters of Bareges and
Cauterets appear to belong to this flrft order,
and thofe of St. Amant, Aix la Chapelle,
and Montmorency, appear to belong to the
fecond. Moftof thefe waters are thermal; but
that of Enghien, near Montmorency, is cold.

Class IV. Ferruginous Waters.

Iron being the mod abundant of metals,
and the molt fufceptible of alteration, it is
not to be wondered at that water eafily be-
comes charged with it, and confequently
that the ferruginous waters are the rnoft

abundant

MINERAL WATERS. 457

abundant and moft common of all mineral
waters. Modern chemiftry has thrown great
light on this clafs of waters -> they were for-
merly fuppofed to be all vitriolic. M.
Monnet has afcertained that moft of them
do not contain vitriol, and he fuppofed that
the iron is diflblved without the inter-
medium of an acid. It is at prefent known,
that the iron is not in the (late of vitriol,
but is diflblved by means of the cretaceous
acid, and forms the fait which we have called
chalk of iron. Meflrs. Lane, Rouelle, Berg-
man, and many ether chemifts, have put
this out of doubt. The greater or lefs quan-
tity of cretaceous acid, and the ftate of the
iron in waters of this kind, render it necef-
fary to diftinguifh the prefent clafs into three
orders.

The firft order comprehends martial aci-
dulous waters^ in which the iron is held in
folution by the cretaceous acid, whofe fuper-
abundance renders them brifk and fubacid.
The waters of Buflang, Spa, Pyrmont, Pou-
hon, and la Dominique de Vals, are of this
firft order,

The fecond contains fimple martial wa-
ters, in which the iron is diflblved by the
cretaceous acid, without excefs of the latter.
Thefe waters confequently are not acidulous.
The water of Forges, Aumale and Conde,
as well as the greater number of ferruginous
waters, are of this order; this diftinftion

of

458 THE ANALYSIS OF

of ferruginous, waters was made by M. Du-
chanoy.

But we add a third order, after M.
Monnet, which is that of vitriolic wa-
ters. Though thefe are extremely rare, yet
fome of them are found. M. Monnet has
placed the waters of ParTy in this order. M.
Opoix admits the vitriol of Mars, even in a
confiderable dofe in the waters of Provins.
It is true, that M. de Fourcy denies its ex-
igence, and confiders the iron of thefe waters
as diflblved by fixed air. But no deciiion
can be made refpe&ing this fubjedt, becaufe
the refults of thefe chemifts intirely difagree,
and require new experiments to be made.
It mull be added, that the iron is not found
alone in thefe waters, but is mixed with
chalk, felenite, various muriatic falts, &c.
However, as the metal they contain is the
principal bafis of their properties, they mud
be called martial, in conformity with the
principles we have laid down.*

As to the faponaceous waters admitted by
M. Duchanoy, we muft wait till chemical
and medical experiments have afcertained

* In the euumeration of waters divided into clafles, we
do not mention thofe which may contain arfenic and cop-
per, becaufe they are true poifons. We likewife omit
fuch waters as contain volatile alkali, fal-ammoniac, and
extractive matters produced by the putrefaction of organic
matters on which they have flood. Thefe waters are not
medicinal,

the

MINERAL WATERS. 459

the caufe of their faponaceous property,
which this phyfician attributes to clay ; as
well as of the effects they may produce in the
animal economy, as medicines, by virtue of
this property.

From thefe details we find, that all mine-
ral and medicinal waters are divided into
nine orders, viz.

Cold acidulous waters.

Hot or thermal acidulous waters.

Vitriolic faline waters.

Muriatic faline waters.

Hepatic waters.

Hepatized waters. •

Simple martial waters.

Martial and acidulous waters.

Martial vitriolic waters.

§ IV. The Examination of Mineral Waters,
according to their Phyfical Properties.

After having fhewn the different matters
which may be found in waters, and exhibit-
ed a flight fketch of the method in which
they may be divided into claffes and orders,
according to their principles, it will be necef-
fary to mention the methods of analyfing
them, and difcovering with the greateft pof-
fible degree of accuracy, the fubftances they
hold in folution. This analyfis has been
juftly confidered as the moft difficult part of
chemiftry, fince it requires a perfect know-
ledge of all chemical phenomena, joined to

the

£00 THE ANALYSIS OF

the habit of making experiments. To ob-
tain an accurate knowledge of the nature of
any water, propofed to be examined, i. The
iituation of the fpring, and the nature of the
foil, more efpecially with refpect to mineral
ftrata, muft be carefully obferved ; for this
purpofe cavities may be dug to different
depths, in order to difcover by infpection,
the fubftances with which the water may be
charged. 2. The phyfical properties of the
water itfelf, fuch as its tafte, fmell, colour,
tranfparence, weight, and temperature, muft
next be examined; for this purpofe, two
thermometers which perfectly agree, and a
good hydrometer, muft be provided. Thefe
preliminary experiments require likewife to
be made in the different feafons, different
times of the day, and efpecially in different
ftates of the atmofphere 3 for a continuance of
dry weather, or of abundant rain, has a lin-
gular influence on waters. Thefe firft trials
ufually fhew the clafs to which the water
under examination may be referred, and di-
rect the method of analyfis. 3. The depo-
fitions formed at the bottom of the bafons,
the fubftances which float on the water, and
the matters which rife by fublimation, form
likewife an object of important refearch,
which muft not be neglected. After this
preliminary examination, the proper analyfis
may be proceeded on, which is made after

three

MINERAL WATERS. 46 1

three methods ; by re-agents, by diftillation,
and by evaporation.

§ V, The Examination of Mineral Waters
by Re-agents.

Thefe fubftances, which are mixed with
waters, in order to difcover the nature of
the bodies held in folution by fuch waters,
from the phenomena they prefent, are called
re-agents.

The beft chemifts have always confidered
the ufe of re-agents as a very uncertain me-
thod of difcovering the principles of mineral
waters. This opinion is founded on the
confiderations that their effefts do not deter-
mine in an accurate manner, the nature of
the fubftances held in folution in waters ;
that the caufe of the changes which happen
in fluids by their addition is often unknown :
and that in faft, the faline matters ufually ap-
plied in this analyfis, are capable of produc-
ing a great number of phenomena refpetting
which it is often difficult to form any deci-
fion. For thefe reafons, moft chemifts, who
have undertaken this analyfis, have placed
little dependence on the application of re-
agents. They have concluded, that eva-
poration affords a much furer method of
afcertaining the nature and quantity of the
principles of mineral waters ; and it is taken
for granted, in the beft works on the ana-

. lyfis

462 THE ANALYSIS OF

lyfis of thefe fluids, that re-agents are only
to be ufed as fecondary means, which at moft
ferve to indicate or afford a probable guefs
of the nature of the principles contained in
waters ; and for this reafon, modern analyfts
have admitted no more than a certain num-
ber of re-agents, and have greatly diminifhed
the lift of thofe ufed by the earlier chemifls.
But it cannot be doubted at prefent, that
the heat required to evaporate the water,
however weak it may be, muft produce
fenfible alterations in its principles, and
change them in fuch a manner, as that their
refidues, examined by the different methods
of chemiftry, mall afford compounds differ-
ing from thofe which were originally held
in folution in the water. The lofs of the
gafeous fubftances, which frequently are the
principal agents in mineral waters, Angu-
larly changes their nature, and befides
caufes a precipitation of many fubftances,
which owe their folubility to the prefence
of thefe volatile matters, and likewife pro-
duces a re-aftion among the other fixed
matters, whofe properties are accordingly
changed. The phenomena of double de-
compofitions, which heat is capable of pro-
ducing between compounds that remain un-
changed in cold water, cannot be eftimated
and allowed for, but in confequence of a long
feries of experiments not yet made. Without
entering, therefore, more fully into thefe con-

fiderations,

MINERAL WATERS. 463

fiderations, it will be enough toobferve, that
this affertion, whofe truth is admitted by
every chemift, fufficiently fhews, that eva-
poration is not intirely to be depended on.
Hence it becomes a queftion, whether
there be any method of aicertaining the pe-
culiar nature of fubftances diffolved in water
without having recourfe to heat; and whe-
ther the accurate refults of the numerous
experiments of modern writers afford any
procefs for corre<3:ing the error which might
arife from evaporation. The following pages
extracted from a memoir communicated by
myfelf to the Royal Society of Medicine,
will mew, that very pure re- agents ufed in
a peculiar manner, may be of much greater
ufe in the analyfis of mineral waters than
has hitherto been thought.

Among the confiderable number of re-
agents propofed for the analyfis of mineral
waters, thofe which promife the moft ufeful
refults are tindture of turnfole, fyrup of
violets, lime-water, pure and cauftic vege-
table alkali, cauftic volatile alkali, oil of
vitriol, nitrous acid, lime-water faturated
with the colouring matter of Pruffian blue,
fpiritous tindlure of nut-galls, and the ni-
trous folutions of mercury and of filver.
Bergman adds to thefe, paper coloured by
the aqueous tindlure of Fernambouc, which
becomes blue by alkalis, the aqueous tinc-
ture of terra merita, which the fame falts con-
vert

460 THE ANALYSIS OF

vert to a brown red, the acid of fugar to ex-
hibit the fmalleft poffible quantity of lime,
and the muriatic fait of ponderous earth to
afcertain the fmalleft quantity of vitriolic
acid.

The effedts and ufe of thefe principal re-
agents have been explained by all chemifts,
but they have not infilled on the neceffity
of their ftate of purity. Before they are
employed, it is of the utmoft importance
perfectly to afcertain their nature, in order
to avoid fallacious efFedts. Bergman has
treated very amply of the alterations they
are capable of producing. This celebrated
chemift affirms, that paper coloured with
the tindture of turnfole becomes of a deeper
blue by alkalis ; but that it is not altered
by the cretaceous acid, which he calls aerial
acid. But as this colouring matter is ufefui
chiefly to afcertain the prefence of this ^cid,
he diredts its tindture in water to be ufed
fufficiently diluted till it has a blue colour.
He abfolutely rejects fyrup of violets, be-
caufe it is fubjedt to ferment, and becaufe
it is fcarcely ever obtained without adultera-
tion in Sweden. M. de Morveau adds in a
note, that it is eafy to diftinguifti a fyrup
coloured by turnfole, by the application of
corrofive fublimate, which gives it a red
colour, while it converts the true fyrup of
violets to a green.

Lime-water is one of the moft ufefui re-
agents

MINERAL WATERS. 465

agents in the analyfis of mineral waters,
though few chemifls have exprefsly men-
tioned it in their works. This fluid de-
compofes metallic falts, efpecially martial
vitriol, whofe iron it precipitates ; it fepa-
rates clay and magnefia from the vitriolic
and muriatic acids, to which thefe fubftan-
ces are frequently united in waters. It like-
wife indicates the prefence of the cretaceous
acid, by its precipitation. M. Gioanetti, a
phyfician of Turin, has very ingenioufly
applied it to afcertain the quantity of cre-
taceous acid contained in the water of St.
Vincent. This chemift, after having ob-
ferved that the volume or bulk of this acid,
from which its quantity has always been
eftimated, muft vary, according to the tem-
perature of the atmofphere, mixed nine
parts of lime-water with two parts of the
water of St. Vincent ; he weighed the cal-
careous earth formed by the combination of
the cretaceous acid of the mineral water
with the lime, and found, according to the
calculation of Jacquin, who proves the ex-
iftence of thirteen ounces of this acid in
thirty-two ounces of chalk, that the water
of St. Vincent contained fomewhat more
than fifteen grains. But as the lime-water
may feize the cretaceous acid united with
fixed alkali, as well *as that which is at li-
berty, M. Gioanetti, to afcertain more
exa&ly the quantity of this laft, made the
Vol. III. G g fame

466 THE ANALYSIS OF

fame experiment with water deprived of its
difengaged acid by ebullition. This pro-
cefs may therefore be employed to deter-
mine, in an eafy and accurate manner, the
weight of difengaged cretaceous acid, con-
tained in a gafeous mineral water.

One of the principal reafons which have
induced chemifts to confider the action of
re-agents in the analyfis of mineral waters
as very fallacious, is, that they are capable
of indicating feveral different fubfiances held
in folution in waters, and that it is then
very difficult to know exactly the effects they
Will produce. This obfervation relates more
efpecially to vegetable alkali, confidered as a
re-agent, becauie it decompofes all the falts
which are formed by the union of acids with
clay, magnefia, lime, and metals. When
this alkali precipitates a mineral water, it
cannot, therefore, be known by fimple in-
fpection of the precipitate, of what nature
the earthy fait, decompofed in the experi-
ment, may be. Its effect is ftill more uncer-
tain when the alkali made ufe of is faturated
with cretaceous acid, as is moft commonly
the cafe ; fince the acid to which it is united
augments the confufion of effects : for this
reafon, I propofe the ufe of very pure cauf-
tic vegetable alkali, which likewife poffeffes
an advantage over the effervefcent alkali,
viz. that of indicating the prefence of chalk
diffolved in a gafeous water, by virtue of

the

MINERAL WATERS. 467

the fuperabundant cretaceous acid ; for it
feizes this acid, and the chalk falls down of
courfe. I have eftablifhed this fadl, by
pouring foap lees newly made, into an arti-
ficial gafeous water, which held chalk in
folution. The latter fubftance is precipi-
tated in proportion as the cauftic fixed alka-
li feizes the cretaceous acid which held it
in folution. By evaporating the filtrated
water to drynefs, I have obtained fait of
foda, ftrongly effervefcent with fpirit of
vitriol. The cauftic fixed alkali likewife
occafions a precipitate in mineral waters,
though they may not qontain earthy falts ;
for if they contain an alkaline neutral
fait, of a lefs foluble nature, the addi-
tional alkali will precipitate it by uniting
with the water, nearly in the fame manner
as fpirit of wine does. M. Gioanetti has
obferved this phenomenon in the waters of
St. Vincent; and it may eafily be ken by
pouring cauftic alkali into a folution of vi-
triolated tartar, or muriate of foda ; thefe
two falts being quickly precipitated.

The cauftic volatile alkali is in general
lefs productive of error, when mixed with
mineral waters ; becaufe it decompofes only
earthy falts, with bafe of clay or magnefia,
and does not precipitate the calcareous falts.
It is neceflary, however, to make two ob-
fervations refpefting this fait : the firft is,
that it muft be exceedingly cauftic, or to-
G g 2 tally

468 THE ANALVSIS OF

tally deprived of cretaceous acid ; without
this precaution, it decompofes calcareous
falts by double affinity : the fecond is,
that the mixture muft not be left expofed
to air, when the effecl: of its action is re-
quired to be infpefted feveral hours after it
is added ; becaufe, as M. Gioanetti has well
obferved, this fait in a very fhort time feizes
the cretaceous acid of the atmofphere, and
becomes capable of decompofing calca-
reous falts. To put this important fact out
of doubt, I made three decifive experi-
ments ; fome grains of felenite, formed of
tranfparent calcareous fpar, and fpirit of
vitriol, were diffolved in diftilled water.
It is neceffary to make the felenite with
tranfparent fpar, becaufe chalk, or Spanifh
white, contain magnefia and river water.
I divided this folution into two parts ; into
the firft I poured a few drops of volatile
alkaline fpirit, recently made, and very
cauftic; this I put into a well-clofed bot-
tle : at the end of twenty-four and forty-
eight hours it was clear and tranfparent,
without any precipitate, and therefore no
decompofition had taken place. The fe-
cond portion was treated in the fame man-
ner with the volatile alkaline fpirit, but
placed in a veffel which communicated with
the air by a large aperture : at the end of a
few hours a cloud was formed near the
upper furface, which continually increafed,

and

MINERAL WATERS. 469

and was at laft precipitated to the bottom.
This depofition eftervefced flrongly with
fpirit of vitriol, and formed felenite. The
cretaceous acid contained in this precipi-
tate was therefore afforded by the volatile
alkali which had attracted it from the at-
mofphere. This combination of cretaceous
acid and alkaline gas, forms ammoniacal
chalk, capable of decompofing calcareous
falts by double affinity, as Black, Jacquin,
and many other chemifts have fliewn, and
as may be eafily proved, by pouring a folu-
tion of concrete volatile alkali, or ammo-
niacal chalk, into a folution of felenite,
which is not rendered turbid by the cauf-
tic volatile alkali. Laftly, to render the
theory of this fecond experiment clearer, I
took the firft portion to which the cauftic
volatile alkali had been added, and which
having been kept in a clofe veffel, had loft
no part of its tranfparency. I reverfed the
bottle which contained it, over the funnel
of a very fmall pneumato-chemical appa-
ratus, and by the affiftance of a fyphon, I
pafTed into it cretaceous acid gas difengaged
from the effervefcent fixed alkali by fpirit
of vitriol. In proportion as the bubbles of
this acid paffed through the mixture, it
became turbid in the fame manner as lime-
water : by filtration a precipitate was fepa-
rated, which was found to be chalk, and
the water by evaporation, afforded ammo-
G g 3 niacal

47^ THE ANALYSIS OF

niacal vitrriol : gafeous water, or the acid
fpirit of chalk, produced the fame decom-
pofition in another mixture of pure felenite
and cauftic volatile alkali. This decifive
experiment clearly fhews, that the volatile
alkali decompofes felenite by double affi-
nity, and by means of the cretaceous acid.
Hence we fee, that when it is required to
preferve a mixture of the mineral water
with volatile alkali for feveral hours, (which
is fometimes neceflary, becaufe it does not
decompofe certain earthy falts but very
ilowly) the experiment muft be made in
a veflel which can be accurately clofed, in
order to prevent the contaft of air, which
would falfify the refult. This precaution,
which is of great importance in the ufe of
all re-agents, is likewife mentioned by
Bergman and Gioanetti. To thefe I fhall
add another obfervation concerning the ufe
of volatile alkali. As it is a matter of con-
fiderable difficulty to preferve the volatile
alkali in the ftate of perfedt caufticity,
though it is neceflary to be had in fuch a
ftate, for the analyfis of mineral waters,
a very fimple expedient, which I have often
ufed with fuccefs, may be applied in this
cafe. It is to pour a fmall quantity of vola-
tile alkaline fpirit into a retort, whofe neck
is plunged in the mineral water : when the
retort is flightly heated, the alkaline gas
becomes difengaged, and paffes highly cauf-
tic

MINERAL WATERS. 47I

tic into the water. If it occafions a preci-
pitate, it may be concluded that the mine-
ral water contains martial vitriol, which
may be known by the colour of the preci-
pitate, or otherwife that it contains falts,
with bafe of aluminous or magnefian earth.
It is difficult to determine from the phyfical
properties of the earthy precipitate formed
in waters by the cauftic volatile alkali, to
which of the two laft bafes it is to be at-
tributed ; yet the manner in which it is
formed may ferve to decide. Six grains of
Epfom fait were diflblved in four ounces
Of diftilled water, and fix grains of alum in
an equal quantity of the fame fluid: through
each of thefe folutions a fmall quantity of
alkaline gas was pafled : the folution of
Epfom fait immediately became turbid,
while that of alum did not begin to exhi-
bit a precipitate till twenty minutes after.
Thefe mixtures were carefully included in
well-clofed bottles. The fame phenomenon
took place with the nitres and muriates of
magnefia and aluminous earth, diftblved in
equal quantities of diftilled water, and treated
in the fame manner. The quicknefs or
flownefs of the precipitation of a mineral
water, by the addition of alkaline gas,
therefore affords the means of afcertaining
the nature of the earthy fait decompofed by
this gas. In general, falts with bafe of
magnefia, are much more ufually met with
G g 4 than

47* THE ANALYSIS OF

than thofe with bafe of aluminous earth.
Bergman has obferved, that the volatile al-
kali is capable of forming with vitriol of
magnefia or Epfom fait, a compound, in
which a portion of this neutral fait is com-
bined, without decompolition, with a por-
tion of ammoniacal vitriol. This non-
decompofed portion of Epfom fait, may
probably form with the ammoniacal vitriol
a mixed neutral fait, fimilar to fal alembroth.
The volatile alkali does not, therefore, pre-
cipitate the whole of the magnefia, and con-
fequently does not accurately exhibit the
quantity of Epfom fait, of which that earth
is the bafe. For this reafon lime-water, in
my opinion, is preferable for afcertaining
the nature and quantity of falts with bafe
of magnefia contained in mineral waters. It
has likewife the property of precipitating the
falts with argillaceous bafe much more abun-
dantly and readily than alkaline gas.*

The concentrated vitriolic acid precipi-
tates a white powder from water which
contains ponderous earth, according to
Bergman; but, as the fame chemift obferves,

* It may be obferved, that I repeat many facts already
explained in the courfe of this work, which I have thought
proper to do, in order to render this fmall treatife on the
analyfis of mineral waters more perfpicuous and com-
plete, and to collec"t, in one view, all the knowledge which
appears to be indifpenfably necefTary to be poflefTed by fuch
as undertake this fpecies of analyfis.

that

MINERAL WATERS. 473

that this earth is feldom found in mineral
waters, it will not be neceffary to enlarge on
the effects of this re-agent. When it pro-
duces an effervcfcence or bubbles in water,
it indicates the prefence of chalk, cretace-
ous fixed alkali or pure cretaceous acid: each
of thefe fubftances may be distinguished by
certain peculiar phenomena. If water con-
taining chalk be heated after the addition of
the vitriolic acid, a pellicle and depofition of
felenite are foon formed, which does not
happen with waters which are fimply alka-
line. At firft confideration, it may feem that
the felenite ought to be precipitated as foon
as the vitriolic acid is poured into water con-
taining chalk -, this, however, very feldom
happens without the affiftance of heat, be-
caufe thefe waters moft commonly contain a
fuperabundance of cretaceous acid which
favours the folution of the felenite, and of
which it is neceflary to deprive them be-
fore the fait can be precipitated. This fact
may be (hewn, in the cleared manner, by
pouring a few drops of concentrated vi-
triolic acid into a certain quantity of lime-
water which has been precipitated, and
afterwards rendered clear by the addition of
cretaceous acid ; if the lime-water be
highly charged with regenerated chalk, a
precipitate of felenite is thrown down in
a few minutes, or more flowly in propor-
tion as the cretaceous acid is fet at liberty.

If

474 THE ANALYSIS OF

If no precipitate be afforded by (landing, as
will be the cafe when the quantity of felenite
Is very fmall, and the fuperabundant creta-
ceous acid confiderable, the application of a
flight degree of heat will caufe a pellicle of
felenite, and a precipitate of the fame nature
to be formed.

The fmoking fpirit of nitre is recom-
mended by Bergman to precipitate fulphur
from hepatized waters. The experiment
may be made by pouring a few drops of
the fmoking fpirit on diftilled water, in
which the gas difengaged from cauftic liver
of fulphur, heated in a retort, has been re-
ceived. This artificial hepatic water, which
does not confiderably differ from natural
fulphureous waters, except in the circum-
ftance of its being more difficult to filter, and
its always appearing fomewhat turbid, affords
a precipitate in a few feconds, by the addi-
tion of nitrous acid ; the precipitate is of a
yellowifh white ; when collected on a fil-
ter and dried, it burns with the flame and
fmell of fulphur, and in other refpefts has
every character of that inflammable body.
The fpirit of nitre feems to alter hepatic gas
in the fame manner as it does all other in-
flammable fubflances, by virtue of the great
quantity of pure air it contains. Scheele
has recommended the dephlogifticated mu-
riatic acid to precipitate the fulphur, from
waters of this nature, but it did not pro-
duce

MINERAL WATERS, 47$

duce this effect on the waters of Enghien ;
and I have difcovered that the fulphureous
acid precipitates fulphur with great facility.
There are few re-agents, whofe mode of
action is lefs known than that of the phlogif-
ticated alkali ; it has been long fince afcer-
tained, that this liquor prepared with bul-
lock's blood, contains Pruffian blue ready
formed -, it has been thought that this blue
might be feparated by the addition of an
acid; and in this flate it has been propofed
as a fubftance capable of exhibiting iron ex-
iting in mineral waters. Whether it be true
or not, that the colouring matter of Pruffian
blue is contained in phlogifticated lixivium,
as Bucquet fuppofed, and Mr. Baunach has
fince afcertained ; it feems clear that this
lixivium ought to be excluded from the
clafs of re-agents. Macquer having dif-
covered that Pruffian blue is decompofed by
alkalies, propofed the faturated liquor of the
colouring matter of this blue, as a teft to
afcertain the prefence of iron in mineral
waters. But as the liquor itfelf likewife con-
tains a fmall quantity of Pruffian blue, which
may be feparated by means of an acid, as
Macquer has mewn, M. Baume advifes
that two or three ounces of diftilled vinegar
be added to each pound of this Pruffian
alkali, and digefted in a gentle heat, till
the whole of the Pruffian blue is preci-
pitated; after which pure fixed alkali is to

be

476 THE ANALYSIS OF

be added to faturate the acid of vinegar.
Notwithstanding this ingenious procefs, I
have obferved, that the Pruffian alkali puri-
fied by vinegar depofits Pruffian blue, in
procefs of time, more efpecially by evapo-
ration. M. Gioanetti made the fame ob-
fervation by evaporating the Pruffian alkali,
purified by the method of Baume, to dry-
nefs : he has propofed two proceflfes for ob-
taining this liquor in a ftate of purity, and
totally exempt from iron; the one confifts
in fuperfaturating the Pruffian alkali with
diftilled vinegar, evaporating it to drynefs
by a gentle heat, diftolving the remaining
mafs in diftilled water, and filtrating the
folution ; all the Pruffian blue remains on
the filter, and the liquor, which paries
through, contains none at all. The other
procefs confifts in neutralizing this alkali
with a folution of alum, from which, after
filtrating, the vitriolated tartar, is feparated
by evaporation. Thefe two liquors do not
afford a particle of Pruffian blue with the
pure acids, nor by evaporation to drynefs.
The lime-water, faturated with the colour-
ing matter of Pruffian blue, mentioned by
us, in treating on iron, does not require
thefe preliminary operations : when poured
on a folution of martial vitriol, it imme-
diately forms pure Pruffian blue without
any mixture of green. Acids do not preci-
pitate any Pruffian blue from this re-agent ;

it

MINERAL WATERS. 477

it therefore does not contain iron, and con-
fequently is preferable to the Pruffian alka-
lies, in the aflay of mineral waters. This
phenomenon doubtlefs depends on the adlion
of the lime, which, when diflblved in water,
is far from having the fame efficacy on iron as
alkalies have. This Pruffian lime-water feems
to be exceedingly well adapted to diftinguifh
martial waters, whether they be gafeous
or vitriolic. In fadt, the cretaceous gas,
which holds iron in folution in waters,
being of an acid nature, decompofes Pruffian
lixiviums by the way of double affinity, as
well as martial vitriol. I have tried Pruffian
lime-water on Spa-waters, and thofe of Pafly,
and I immediately obtained a very percep-
tible blue in the former, and very abund-
ant in the latter. This, therefore, is a liquor
very eaiily prepared, which does not contain
the fmalleft portion of Pruffian blue, and is
exceedingly well calculated to exhibit the
prefence of fmall quantities of iron in waters.
It is a kind of neutral fait, formed by the
colouring part of the blue and lime. I have
obferved, in the foregoing part of this work,
in treating of iron, that M. Scheele made the
fame inferences as myfelf concerning the
utility of this proof liquor, which was men-
tioned by me as early as the year 1780.

Nut-galls, as well as all other rough and
aflringent vegetables, fuch as oak-bark, the
fruit of thecyprefs tree, the hulks of nuts, &c.

have

47$ THE ANALYSIS OP

have the property of precipitating folutions
of iron, and exhibiting that metal of dif-
ferent colours, according to its quantity,
its ftate, and that of the water in which it
is diflblved. This colour in general is of all
fhades, from a pale rofe to the deepelt black.
It is well known that the purple colour,
aflumed by waters, with the tinfture of
nut-galls, is not a proof that they contain
iron in its metallic flate, fince martial vitriol
and iron united to the cretaceous acid,
which is called martial chalk, likewife af-
fume a purple colour by the infufion of .nut-
galls. The differences of colour obferved in
thefe precipitations, as M. Duchanoy has
well obferved in his Effays on the Art of Imi-
tating Mineral Waters, depend rather on
the quantity of iron, its greater or lefs degree
of adhefion to the water, and the more
or lefs advanced flate of decompofition of
the folution. We may here take notice,
that though this re-agent has been known
and employed with fuccefs in the analyfis of
mineral waters fince the time that Duclos
recommended it in 1667, and though Mac-
quer, Monnet, and the chemifts of the
academy of Dijon have made a great number
of experiments on nut-galls, the nature of
the aftringent principle is not yet known*
We can only conjecture that it is a pe-
culiar acid, fince it unites with alkalies,
converts blue vegetable colours to a red,

decompofes

MINERAL WATERS. 479

decompofes liver of fulphur, and combines
with metallic calces. Nut-galls in powder,
the infufion of this fubftance in water, made
without heat, and the tincture of fpirit of
wine, are ufed to afcertain the prefence of
iron in mineral waters. The tindture is
preferred, becaufe it is not fubjedt to become
mouldy as the aqueous folution is. It is a
Angular circumftance, that the diftilled pro-
ducts of nut-galls likewife colour martial
iblutions. The infufions in acids, alkalies,
oils, and ether, exhibit the fame phenome-
non. The iron precipitated by this matter
from acids, is in a flate little known, and
forms a kind of neutral fait, which though
very black, is not attradted by the magnet.
It diflblves flowly, and without fenfible ef-
fervefcence in acids, but lofes thefe proper-
ties by the adtion of fire, and is then at-
tradted by the magnet. The nut-gall is fo
efficacious a re-agent, that a fingle drop of
its tindture colours in the fpace of five mi-
nutes, with a purple tinge, three pints of
water, which contains only the twenty-fifth
part of a grain of martial vitriol.

The two laft re-agents we fhall propofc
for the examination of waters, are folutions
of filver and of mercury in the nitrous acid.
Thefe have ufually been employed to exhi-
bit the prefence of the vitriolic or muriatic
acids in mineral waters; but many other fub-
ftances, which do not contain the fmallefl

portion

400 THE ANALYSIS OF

portion of thofe, are likewife precipitated
by thefe folutions. The white and heavy
ftrias which the folution of filver exhibits in
water, that contains no more than half a
grain of marine fait in the pint, afcertains*
the prefence cf the marine acid with great
certainty and facility •, but they do not in
the fame manner indicate the prefence of
the vitriolic acid, fince, according to Berg-
man's eftimate, at leaft thirty grains of vi-
triol of foda mull exift in the pint of
water, in order to produce an immediate
fenfible effect. To this we may add, that
fixed alkali, chalk, and magnelia, precipi-
tate the nitrous folution of filver in a much
more evident manner, and confequently that
the precipitation formed in a mineral water
by this folution is inefficient to determine
with precifion, the faline or earthy fub-
ftances from which it arofe.

The folution of mercury by the nitrous
acid, is ftill more productive of error : it not
only indicates the prefence of vitriolic and
muriatic acids in waters, but it is like-
wife precipitated by the cretaceous fixed al-
kali, in a yellowifh powder, which might
be miftaken for an effect of the vitriolic
acid. Lime and magnefia produce a preci-
pitate nearly of the fame appearance. It has
been commonly fuppofed, that the very
abundant white precipitate which it forms
in water, is owing to the prefence of marine

fait*

MINERAL WATERS. 481

fait; yet mucilaginous and extractive fub-
ftances exhibit the fame phenomenon, as is
now well known to all chemifts. Befides,
thefe fources of error and uncertainty, de-
pendant on the property which feveral fub-
ftances have, of producing fimilar precipitates
with the nitrous folution of mercury, there
are likewife others which depend en the
ftateofthis folution itfelf, and of which it
is of the utmoft confequence to know, in
order to avoid very confiderable errors in the
analyfis of waters. Bergman has mention-
ed fome of the remarkable differences ob-
ferved in' this folution, according to the
manner in which it is made, either with or
without heat, more particularly with refpedt
to the colour the precipitates it affords by
different intermediums ; but he does not
fay a word concerning the property this fo-
lution poffeffes, of being precipitated by dif-
tilled water, when it is highly charged with
calx of mercury ; though M. Monnet men-
tioned this facl: in his treatife on the diffolu-
tion of metals. The importance of this
fubject renders it neceffary to enter more
fully into the circumftances which attend
it. I have made a great number of folu-
tions of mercury, in very pure nitrous acid,
with different dofes of thefe two fubftances,
with heat and in the cold, and with acids of
very different ftrengths. Thefe experiments
have afforded the following refults.
Vol. III. H h i. Solu-

482 THE ANALYSIS OF

1. Solutions made in the cold, became
charged more or lefs readily with different
quantities of mercury, according to the de-
gree of concentration of the nitrous acid 3 but
whatever the quantity of mercury diffolved
in the cold by the concentrated acid may be,
no part of it will be precipitated by mere
water. I have diffolved in the cold two
drachms and a half of mercury, in two
drachms of fmoking fpirit of nitre, weigh-
ing one ounce, four drachms, and five grains,
in a bottle, which contained an ounce of
diftilled water : the combination took place
with the utmoft rapidity; very denfe ni-
trous gas efcaped, together with aqueous
vapours, diffipated by the heat of the mix-
ture, amounting to more than one fourth
of the acid. This folution was of a deep
green, and very tranfparent. I poured a few
drops into half an ounce of diftilled water :
fome white ftriae were formed, which were
diffolved by agitation, and afforded no preci-
pitate, though it was the moft faturated fo-
lution I could make in the cold, and prefent-
ed the greater!: degree of commotion, effer-
vefcence, and red vapours, during the com-
bination of the mercury and acids. As it had
depoiited cryftals, I added two drachms of
diftilled water, which diflblved the whole
without any appearance of precipitation.
With much greater fafety therefore may
fuch folutions, as have been made in the

cold

MINERAL WATERS. 483

Cold With common nitrous acid, and half
their weight of mercury, be ufed in the
analyfis of mineral waters, for they will
never afford a precipitate by the addition of
mere water.

2. The weakeft nitrous acid ftrongly
heated on mercury, will diffblve a larger
quantity than the ftrongeftacid in the cold :
the folution, which is of a light yellow co-
lour, will appear thick and oily, and will af-
ford by (landing, an irregular yellowifh mafs,
which may be changed intoa beautiful turbith
by the addition of boiling water; this fo-
lution poured into diftilled water, forms a
very abundant precipitat(B,of a yellow colour,
fimilar to turbith. A folution made in the
cold, exhibits the fame refult, if it be ftrong-
ly heated, fo as to difengage a large quan-
tify of nitrous gas. Thefe folutions made
with heat, ought therefore to be excluded
from the analyfis of mineral waters, becaufe
they are decompofable by diftilled water.

3. The two folutions appear to differ
from each other in the quantity of calx of
mercury, which is much greater in that
which is precipitated by the water, than in
that which is not decompofable by thatfluid*
I have proved this, by evaporating equal
quantities of both thefe folutions in an apo-
thecaries phial, to reduce them into red
precipitate, and I obtained one fourth more
of this precipitate from the folution, which

H h 2 is

484 THE ANALYSIS OF

is decompofed by water, than from that
which is not rendered turbid. The fpecific
gravity likewife appeared to me to be a good
method of afcertaining the relative quanti-
ties of calx of mercury contained in thefe
different fluids. I compared weights of
equal mafles of three mercurial nitrous
folutions; the one, which was not at all
precipitated by diftilled water, and was the
refult of the firft mentioned experiment,
weighed one ounce, one drachm, and fixty-
feven grains in a bottle, which contained
exactly an ounce of diftilled water. The
fecond folution was made by a very gentle
heat, and produced a flight opal colour with
diftilled water, and fcarcely any fenfible
quantity of precipitate. The fame bottle
contained one ounce fix drachms twenty-
four grains. Laftly, a third mercurial folu-
tion confiderably heated, and which preci-
pitated a true turbith mineral of a dirty yel-
low, by diflilled water, weighed in the fame
bottle, one ounce, {even drachms, twenty-
five grains.* A decifive experiment remain-
ed to be made to confirm this opinion ftill
more perfectly : if the folution precipitated
by water, owed this property to a quantity
of mercurial calx, too large with refpect to
the acid, it would of courfe lofe that pro-
perty by the addition of acid ; this accord-

* The above weights are French ounces, gros, and
grains, and the fpecific gravities of the three folutions of
mercury are refpe&ively 1.24; 1.74; and 1.95 with refpecl:
to diftiUec} water taken as unity, T,

ingly

MINERAL WATERS. 485

ingly happened. Aqua fortis was poured on
a folution which was decompofed by water,
and it foon acquired the property of no lon-
ger being precipitated, and was abfolutely
in the lame ftate as that which had been
made flowly at firft, by the mere heat
of the atmofphere. M. Monnet has men-
tioned this procefs, as a means of prevent-
ing cryftals of mercurial nitre from becom-
ing converted into turbith by the contact of
the air. It is by a contrary procefs, and by
evaporating a portion of the acid of a good
folution, which is not precipitated by water,
that it is converted into a folution much
more ftrongly charged with mercurial calx,
and confequently capable of being decom-
pofed by water; its original property may be
reftored by the addition of a quantity of acid,
equal to that which it loft by evaporation.

Such are the different confiderations which.
I have thought it neceffary to exhibit, that
the effects of re-agents on waters may be.
better afcertained; but whatever may be the
degree of precifion to which refearches of
this nature may be carried ; however exten-
live the knowledge we may have acquired
concerning the degrees of purity, and the
different ftates of fuch fubftances as are com-
bined with mineral waters, for the purpole
of difcovering their principles, if it ftill re-
mains a fact that each of thefe re-agents is
capable of indicating two or three different
fuiftances diffolved in thefe waters, the re-
H h 3 iiilt

486 THE ANALYSIS OF

fult of their adtion will always be fubjeft to
uncertainty. Lime, for example, feizes the
cretaceous acid, and precipitates falts with
the bafe of clay, and of magnefia, as well as
the metallic falts. Volatile alkali produces
the fame effedt. Fixed alkalies, befides
the above-mentioned falts, precipitate thofe
with bafe of lime. Lime-water charged
with the colouring matter of Pruffian blue,
Pruffian alkali, and the fpirituous tindture of
nut-galls, precipitate martial vitriol and mar-
tial chalk. The nitrous folutions of filver
and of mercury, decompofe all the vitriolic
and muriatic falts, which may be various
both in quantity and in kind, in the fame
water, and are themfelves decompofable by
alkalies, chalk, and magnefia. Among this
great number of complicated effedts, how
fhall we diftinguifh that which takes place
in the water under examination, or by what
means fhall we afcertain whether it is fimple
or compounded ?

Thefe queftions, though very difficult, for
the time when the expedients of chemiftry
were little known, are neverthelefs capable
of being difcuffed in the prefent ilate of our
knowledge. I mull firft obferve, that the
nature of re-agents being much better known
at. prefent than it was fome years ago, and
their re-adlion on the principles of water
better afcertained, it may, therefore, be
iTxongly prefumed that their application may

be

MINERAL WATERS. 487

be much more advantageoufly made than has
hitherto been fuppofed: neverthelefs, among
the great number of excellent chemifts who
have attended to the analyfis of waters,
MefTrs. Baume, Bergman, and Gioanetti,
are almoft the only perfons who have been
aware of this great advantage. We have been
long in the habit of examining mineral
waters by re-agents, in very fmall dofes, and
often in glaffes : the phenomena of the pre-
cipitations obferved have been noted down,
and the experiment carried no further. M.
Baume advifes, in his chemiftry, that a con-
liderable quantity of the mineral water, under
examination, fhould be faturated with fixed
alkalies and with acids, that the precipitates
be collefted, and their nature examined.
Bergman apprehended that the quantity of the
principles contained in waters might be
judged of from the weight of the precipitates
obtained in thefe mixtures. Several other
chemifts have likewife employed this method,
but always with a view to certain particular
circumftances ; and no one has hitherto
propofed to make a connected analyfis of
mineral waters by this means. To fucceed in
this analyfis, I think it would be proper to
mix feveral pounds of the mineral water with
each re-agent, till the latter ceafes to pro-
duce any precipitate ; the precipitate fhould
then be fuifered to fubfide during the time

H h 4 of

488 THE ANALYSIS OF

of twenty-four hours, in a veffel accurately
clofed ; after which the mixture being filtered,
and the precipitate dried and weighed, the
operator may proceed to examine it by the
known methods. In this manner the nature
of the fubftance will be clearly afcertained, on
which the re-agent has adted, and the caufe
of the decompofition may confequeritly be
inferred. A certain order may be followed
in thefe operations, by mixing the waters firft
with fuch fubftances as are leaft capable of
altering them, and afterwards paffing to
other fubftances capable of producing changes
more varied and difficult to explain. The fol-
lowing method is that which I commonly ufe
in this kind of analyfis. After having exa-
mined the tafte, the colour, the weight, and
all the other phyfical properties of a mine-
ral water, I pour four pounds of lime-water
on an equal quantity of the fluid ; if no pre-
cipitate is made in twenty-four hours, lam
fure that the water contains neither the cre-
taceous acid at liberty, nor the cretaceous
fixed alkali, nor earthy falts with the bafe
of aluminous earth or magnefia, nor metallic
falts. But if a precipitate be formed, I fil-
ter the mixture, and examine the chemical
properties of the depofited fubftance ; if it
has no tafte, if it be infoluble in water, or
effervefces with acids, or forms an infipid
and almoft infoluble fait by the addition of
•vitriolic acid, I conclude that it is chalk,

and

MINERAL WATERS. 489

and that the lime-water has acfted only, on
the cretaceous acid dirTolved in the water.
If, on the contrary, it is fmall in quantity,
and fubfides very flowly; if it do not ef-
fervefce, and affords with the vitriolic acid
a ftyptic fait, or a bitter and very foluble
fait, it is formed by magnefia or aluminous
earth, and often by both. I need not enter
at large into the means of diftinguifhing
thefe two fubftances from each other, as
they are fufliciently explained in the fore-
going part of this work. I (hall only add,
that a fuftkient number of experiments
ought to be made, to leave no doubt refpect-
ing their nature.

After the examination by lime-water, I
pour on four other pounds of the fame mi-
neral water, a drachm or two of volatile al-
kaline fpirit, perfectly cauftic, or I caufe
alkaline gas, difengaged by heat from the
fpirit, to pafs into the water. When the
water is faturated, I leave it at reft in a clofe
vefiel for twenty-four hours ; if a precipi-
tate be afforded, it can only confift of mar-
tial or magnefian, or aluminous falts, whofe
nature I examine by the different methods
mentioned in the foregoing paragraph. But
the adlion of alkaline gas being more falla-
cious than that of lime-water, which produces
the fame decompofitions, it muft be obferv-
ed that this laft fhould only be ufed as an
affiftant means, which does not afford refults

equally

490 THE ANALYSIS OF

equally accurate with thofe produced by the
former re-agent.

When falts with bafe of aluminous
earth, or magnefia, have been difcovered by
lime-water, or by alkaline gas, the cauftic
mineral alkali may be ufed, to diftinguifh
thofe with bafe of lime, fuch as felenite and
calcareous marine fait : for this purpofe I
precipitate fome pounds of the water, which
I examine by this alkaline liquor, till it no
longer produces any turbidnefs. As this
alkali decompofes falts with bafe of alu-
minous earth, as well as thofe compofed
of lime : if the precipitate refembles in its
form, colour, and quantity, that which
lime-water has afforded, it may beprefumed
that the water does not contain calcareous
fait, and the chemical examination of the
precipitate ufually confirms this fufpicion ;
but if the mixture is much more turbid
than that made with lime-water ; if the de^
pofition be much heavier, more abundant,
and more readily afforded, the lime is mixed
with magnefia or aluminous earth. I af-
certain this by treating the precipitate after
the different methods before explained. It
may eafily be concluded, that iron precipi-
tated by re- agents, at the fame time as the
falino-terreftrial fubftances, is eafily known
by its colour and its tafte; and that the fmall
quantity of this metal feparated in thefe pro-
ceffes, is not fufficient to affetf: the refults.

It

MINERAL WATERS. 49 I

It were ufelefs to explain at large, the ef-
fects of oil of vitriol, fpirit of nitre, nuU
galls, alkali, or lime faturated with the colour-
ing matter of Pruffian blue, employed in re-
agents or mineral waters. The general ac-
count of thefe effects given in this appendix
may fuflice ; I fhall therefore only add, that
when they are mixed in large dofes with
thefe waters, and the precipitates collected,
the nature and quantity of their principles,
may be more accurately afcertained, as has
been done by Meffrs. Bergman and Gioanetti.

Neither fhall I dwell on the products
which the nitrous folutions of filver or mer-
cury afford when mixed with mineral wa-
ters. It is more particularly neceffary to
operate with large quantities of water, when
thefe re-agents are ufed, in order to determine
the nature of the acids contained in the
waters. The analyfis of thefe fluids will be
complete when their acids are known, be-
caufe thefe are often combined with the bafes
exhibited by the re-agents before-mentioned.
The colour, the form, and the abundance of
the precipitates afforded by the nitrous fo-
lutions of mercury and filver, have hitherto
exhibited to chemifts the nature of the acids
which caufed them. A thick and ponderous
depofition immediately formed by thefe fo-
lutions, denotes the muriatic acid : if it is
fmall in quantity, white, and cryftallized
with the nitre of filver, or yellowifh, and

yellow

492 THE ANALYSIS OF

yellow and irregular when formed with that of
mercury, and if it fubfide but flowly, it is at-
tributed to the vitriolic acid. But, as thefe
two acids are often met with in the fame water,
and as alkali and chalk likewife decompofe
the folutions, the refults or deductions made
from the phyfical properties of the precipi-
tates muft be uncertain. It is therefore ne-
ceffary to examine them more effectually ;
for this purpofe, lunar, or mercurial folu-
tions may be mixed with five or fix pounds
of the water intended to be analyzed. The
mixtures being filtered, twenty-four hours
after, the precipitates muft be dried, and
treated according to the methods of che-
miftry. If the precipitate afforded by the
nitrous folution of mercury be heated in a
retort, the portion of metal united with the
muriatic acid of the waters will be volatilized
into mercurius dulcis, and thatwhich is com-
bined with the vitriolic acid will remain at
the bottom of the veffel, and exhibit a red-
difh colour. Thefe two falts may likewife be
diftinguifhed by putting them on a hot coal:
the vitriol of mercury, if prefent, emits
a fulphureous acid, andaflumes a red colour;
the mercurial muriate remains white, and is
volatilized without exhibiting any fmell of
fulphur. Thefe phenomena likewife ferve
to diftinguiih the precipitates which may be
formed by the alkaline fubftances contained
in water, (ince the latter do not emit the

fulphureous

MINERAL WATERS. 493

fulphureous fmell, and are not volatile with-
out decompofition.

The precipitates produced by the combi-
nation of mineral waters with the nitrous
folution of filver, may be as eafily examined
as the foregoing. Vitriol of filver being
more foluble than lunar cornea, diftilled wa-
ter may be fuccefsfully ufed to feparate thefe
two falts. Luna cornea is known by its
fixity, its fufibility, and efpecially in its be-
ing lefs eafily decompofable than vitriol of
filver. This laft, placed on hot coals, emits
a fulphureous fmell, and leaves a calx of
filver, which may be fufed without addition.
I do not here fpeak of all the procefles che-
miftry affords for feparating or diftinguiih-
ing the two lunar falts here mentioned : it
is fufficient that I have pointed out fome of
them.

§ VI. The Examination of the Mineral
Waters by Diftillation.

Diftillation is ufed in the analyfis of wa-
ters, to afcertain the gafeous fubftances they
may be united to. Thcle fubftances are ei-
ther air, more or lefs pure, or cretaceous
acid, or hepatic gas. To afcertain their na-
ture and quantity, fome pounds of the mine-
ral water muft be poured into a retort, fuf-
ficiently large to contain it, without being
filled more than half or two-thirds of its
I capacity;

494 TIiE ANALYSIS Ofr

capacity; to this veffel a recurved tube is to
be adapted, which paffes beneath an inverted
veffel filled with mercury. In this difpo-
fition of the apparatus, the retort muft
be heated till the water perfectly boils, or
till no more elaftic fluid paffes over. When
the operation is finifhed, the quantity
of air contained in the empty fpace of the
retort muft be fubtraded from the bulk of
the gas obtained ; the reft confifts of aeri-
form fluid, which was contained in the mi-
neral water, whofe properties may quick-
ly be known by the proofs of a lighted taper,
tindture of turnfole, and lime-water ; if it
catches fire, and has a fetid fmell, it is he-
patic gas ; if it extinguishes the taper, red-
dens turnfole, and precipitates lime-water,
it is the cretaceous acid -y laftly, if it main-
tains combuftion without taking fire, is
without fmell, and alters neither turnfole
nor lime-water, it is atmofpheric air. It
may happen that the elaftic fluid may be
purer than the air of the atmofphere : in this
cafe its degree of purity may be judged by
the manner in which it maintains combuf-
tion, or by mixing it with nitrous or in-
flammable gas, in the eudiometers of Fon-
tana and Volta. The procefs ufed in ob-
taining gafeous matters, contained in lime-
water, is intirely modern. A moiftened
bladder was formerly ufed, which was adapt-
ed to the neck of a bottle filled with mineral

water 5

MINERAL WATERS. 495

water ; the fluid was agitated, and by the
fwelling of the bladder, an eftimate was made
of the quantity of gas contained in the wa-
ter. This method is now known to be fal-
lacious, becaufe water cannot give out all its
gas but by ebullition, and becaufe the fides
of the moiftened bladder alter and decom-
pofe the elaftic fluid obtained. It is fcarcely
neceflary to remark, that the phenomena ex-
hibited by the water, during the efcape of
the gas, muft be carefully examined, and
that a lefs quantity of water may be expofed
to diftillation, in proportion as its tafte
and fparkling indicate that it contains a
larger quantity of gas.

Such is the method recommended by mo-
dern chemifts to obtain the elaftic fluids
combined with waters : I muft obferve, j .
That this procefs cannot be depended on,
with regard to acidulous waters, unlefs the
preflure of the atmofphere, and the ftate of
compreffion of the elaftic fluid under the
glafs veflels, be very accurately accounted
for ; and as this is not eaiily done, the ab-
forption of cretaceous acid by lime-water,
propofed by M. Gioanetti, appears to be
preferable. 2. Though it has been re-
commended by Bergman to obtain hepatic
gas from fulphureous waters, it does not,
anfwer, becaufe the neat of ebullition de-
compofes the gas, and it is likewife de-
compofed by the mercury, which is con-
verted

496 THE ANALYSIS OF

verted into ethiops, as foon as it comes
in contact with this elaftic fluid : for this
reafon, in my analyfis of the waters of Erv-
guien, near Montmorency, I have propofed
litharge to abforb this gas in the cold, and
to deprive hepatized waters of their ful-
phur.

§ VII. The Examination of Mineral Waters
by Evaporation.

Evaporation is generally confidered as the
mofl certain method of obtaining all the
principles of mineral waters. We have be-
fore obferved, and here repeat, that the ex-
periments of Meflrs. Venel and Cornette
fhew that long continued ebullition may de-
compofe faline matters diflblved in water,
and for that reafon we have advifed the ex-
amination of them by re-agents, employed
in greater proportions : yet evaporation may
afford much information, when ufed, toge-
ther with the analyfis by re-agents, which
ought always to be confidered as one of the
principal methods of examining waters.

The intention of evaporation being to
collect the fixed principles contained in
a mineral water, it is obvious, that in
order to know the nature and proportion
of thefe principles, a confiderable quantity
of the water muft be evaporated, and fo
much the more, in proportion as the prin-
ciples

MINERAL WATERS. 497

eiples appear to exift in (mailer quantities*
When the water is thought to contain a large
quantity of faline matter, about twenty
pounds muft be evaporated; if, on the con-
trary, it appears to hold but a very fmall
quantity in folution, it will be neceflary to
evaporate a much larger quantity. It is
fometimes requilite to perform this opera-
tion with feveral hundred pounds. The na-
ture and form of the veflels, in which waters
are expofed for evaporation, is not a mat-
ter of indifference. Thofe of metal, except-
ing filver, are altered by water ; veflels of
glafs, of a certain magnitude, aie veryfubjeci
to be broken ; but thofe of glazed, fmooth
pottery, are the moft convenient, though
the cracks in the glaze fometimes caufe an
abforption of faline matter ; veflels of un-
glazed porcelain, called bifcuit, would doubt-
Icfs be the moft convenient, but their price
is a coniiderable obftacle. Chemifts have
propofed different methods of evaporating
mineral waters ; fome have directed distilla-
tion to drynefs, in clofe veflels, in order to
prevent foreign fubftances, which float in
the atmofphere, from mixing with the re£-
due; but this method is exceflively tedious :
others have advifed evaporation by a gentle
heat, never carried to ebullition, becaufe they
fuppofed that this laft heat alters the fixed
principles, and carries up a portion of them.
This was the opinion of Venell and Bergman.
Vol. III. ' I i M. Mon-

498 ANALYSIS OF

M. Monnet, on the contrary, directs the
water to be boiled, becaufe this motion pre-
vents the reception of foreign matters con-
tained in the atmofphere. Bergman avoids
this inconvenience, by directing the veffel to
be covered, and a hole left in the middle of
the cover for the vapours to pafs out : this
laft method greatly retards the evaporation,
becaufe it diminifhes the furface of the fluid.
At the commencement, the heat ufed muft
be fufficient to repel the duft ; but the great-
eft difference in the manipulation of this ex-
periment, confifts in fome writers dire&ing,
that the fubflances depofited fhould be fe-
parated, as the evaporation proceeds, in or-
der to obtain each pure and by itfelf; others,
on the contrary diredt the operation to be
carried on to drynefs. We are of the opi-
nion of Bergman, that this laft method is
the moft expeditious and certain -, becaufe,
notwithftanding the care which may be
taken, in the firft method, to feparate the
different fubftances, which are depofited or
cryftallized, they are never obtained pure,
and muft always be examined by a fubfequent
analyiis ; and the method is befides inac-
curate, on account of the frequent nitra-
tions, and the lofs it occafions. Laftly, it
is very embarrafling, and fenders the evapo-
ration much longer. Mineral waters may
therefore be evaporated to drynefs, in open
glafs veffels, on the water-bath, or ftill more

advantageoufly

MINERAL WATERS. 499

Advantageoufly in glafs retorts, on a fand-
bath.

Various phenomena are obferved during
this evaporation -> if the water b& acidulous,
it emits bubbles, as foon as the heat firft
begins to act; in proportion as the creta-
ceous acid is difengaged, a pellicle is form-
ed, with a depofition of calcareous earth, or
martial chalk. Thefe firft pellicles are fuc-
ceeded by the cryftallization of felenite; and
laftly, the muriatic falts of pot-afh and fjda
cryftallize in cubes at the furface, but the
deliquefcent are not obtained but by evapo-
ration to drynefs.

The refidue muft then be weighed, and
put into a fmall phial„ with three or four
times its weight of fpirit of wine : the whole
being agitated, and fuffered to fubfide for
fome hours, muft be filtered, and the fpirit
of wine prefei ved feparate. The refidue, on
which the fpirit has not acted, muft be dried
in a gentle heat, or in the open air -> when
perfectly dry, it muft be weighed, and the
lofs of weight will (hew what quantity of cal-
careous or magnefian muriate was contained,
becaufe thefe falts are very foluble in fpirit
of wine. We fhall prefently fpeak of the me-
thod of afcertaining the prefence of thefe two
falts in the fpirituous fluid.

The refidue, after treatment with fpirit of
wine, and drying, muft be agitated with
eight times its weight of cold diftilled water,

I i 2 and

500 ANALYSIS OF

and filtered. After fome hours ftanding, the
refidue is to be dried a fecond time, and boiled
half an hour in four or five hundred times
its weight#of diftilled water : this laft refi-
due, after filtration, confifts of that which
cold and boiling water is inefficient to dif-
folve. The firft water contains neutral falts,
fuch as vitriol of foda, or of magnefia; the
muriate of foda, or the vegetable alkali and
the fixed alkalies, efpecially mineral alkali,
united with cretaceous acid: the large quan-
tity of boiling water fcarcely contains any
fubftance but felenite. There are therefore
four fubftances to be examined, after thefe
different .operations on the matter obtained
by evaporation, i. The refidue infoluble in
fpirit of wine, and in water of different tem-
peratures. 2. The falts diflblved in fpirit
of wine. 3. The falts diflblved in cold wa-
ter. 4, and laftly, Thofe diflblved in boil-
ing water. We fhall now proceed to the
experiments neceflary to afcertain the nature
of thefe different fubftances.

1. The refidue which has refifted the ac-
tion of the fpirit of wine and water, may
be compofed of calcareous earth, of magne-
fian and martial chalk, of clay and of quartz.
Thefe two laft fubftances are feldom found
in waters, but the three firft are very com-
mon ; the brown, or more or lefs deep
yellow colour, indicates the prefence of iron.
If the refidue be of a white grey, it does not

contain

MINERAL WATERS. 50I

contain this metal. When iron is prefent,
Bergman diredts it to be moiftened, and ex-
pofed to the air till it rufts ; in which ftate
vinegar does not adt on it. In order to ex-
plain the methods of feparating thefe differ-
ent fubftances, we will fuppofe an infoluble
refidue to confift of the five fubftances here
mentioned ; it muft firft be moiftened, and
expofed to the rays of the fun; and when the
iron is perfectly rufted, the refidue muft be
digefted in diftilled vinegar. This acid dif-
folves the lime and magnefia, and by evapo-
ration affords the calcareous acetous fait,
diftinguifhable from the acetous fait of mag-
nefia, by its not attracting the humidity of
the air. They may confequently be fepa-
rated by deliquefcence, or by pouring vitri-
olic acid into their folution. The latter
forms felenite, which precipitates; but if the
magnefian acetous fait be prefent, the Epfo'm
fait, compofed of magnefia united with the
vitriolic acid, will remain in folution, and
may be obtained by a well-conducted eva-
poration. To afcertain the quantity of mag-
nefian and calcareous earths contained in this
refidue, the felenite is firft to be precipitated;
and the Epfom fait, formed by the vitriolic
acid poured into the acetous folution, muft
then be precipitated by cretaceous vegetable
alkali. The quantities of thefe precipitates are
known by weighing. When the chalk and
magnefia of the refidue are thus feparated, the

iron,

jJ02 MINERAL WATERS.

iron, the clay, and the quartz remain. The
iron and clay are diffolved by pure muriatic
acid, from which the former is precipitated
from Pruffian lime, and the latter by creta-
ceous vegetable alkali. Thefe precipitates
muft likewife be weighed. The matter which
remains after the feparation of the clay and
iron is ufually quartzofe : its quantity may
be known by weighing, and its habitudes
by fufion with the blow-pipe with cre-
taceous mineral alkali. Such are the moft
accurate procefTes, recommended by Berg-
man, for examining the infoluble refidue of
waters.

2. The fpirit of wine ufed in wafhing
the folid refidue of mineral waters, muft be
evaporated to drynefs. Bergman advifes treat-
ing it with fpirit of vitriol, in the fame man-
ner as the acetous folution before fpoken of;
but it muft be obferved, that this procefs
ferves only to exhibit the bafes of thefe
falts. To determine the acid, which is or-
dinarily united with magnefia or lime, and
fometimes with both, a few drops of oil of
vitriol muft be poured on, which excites an
effervefcence, and difengages the muriatic
acid, known by its fmell and white vapour
when the fait under examination contains
that acid. This may likewife be known by
diflblving the whole refidue in water, and
adding a few drops of the folution of filver.
The nature of the bafe, which, as we have

obferved^

INERAL WATERS. 503

obferved, is either lime, magneiia, or both
together, is known by the fame vitriolic
acid, by a fimilar procefs with that already
explained refpecting the acetous folution.

3. The water ufed in wafhing the firft refi-
due of the mineral water, performed as before
directed, with eight times its weight of cold
diftilled water, contains neutral alkaline
falts, fuch as vitriol of foda, or Glauber's
fait, or muriates or marine falts, chalk of
pot-afh, and of foda, and vitriol of mag-
neiia : a fmall quantity of martial vitriol is
fometimes found. Thefe falts never exifl
all together in waters : the vitriol of foda,
and the chalk of pot-afh, are very fel-
dom found ; but marine fait is frequently
met with, together with cretaceous fo-
da. The vitriol of magneiia is likewife fre-
quently met with, and fome waters even
contain it in confiderable quantities. When
the firft wafhing of the reiidue of a mineral
water contains only one kind of neutral fait,
it may eafily be obtained by cryftallization ;
and its nature afcertained from its form,
tafte, and the action of fire as well as that of
the re-agents: but this cafe is very rare,
for it is much more ufual to find many falts
united in this lixivium. They muft therc-
~fore be feparated, if practicable, by flow
evaporation ; but as this method does not
always perfectly fucceed, however carefully
the evaporation be conducted, it will be ne-

ceflary

504 ARTIFICIAL

ceflary to re-examine the falts obtained at
the different periods of the evaporation.
Cretaceous foda is ufually depofited con-
fufedly with the muriatic falts, but they
may be feparated by a procefs, pointed out
by M. Gioanetti. It confifts in wafhing this
mixed fait with diftilled vinegar ; for this
acid dhTolves cretaceous foda. The mix-
ture muft then be dried and wafhed a fecond
time with fpirit of wine, which takes up
acetous foda, without acling on marine fait.
The fpiritous folution being evaporated to
drynefs, and the refidue calcined, the vine-
gar becomes decompofed and burns. Soda
alone remains, whofe quantity may be then
accurately determined.

4. The water ufed in the quantity of four
or five hundred times the weight of the re-
fiduum of the mineral water contains only
vitriol of lime, or felenite. This may be
afcertained by pure cauftic volatile alkali,
which occafions no change, while the cauftic
vegetable alkali precipitates it abundantly.
By evaporation to drynefs, the quantity of
earthy fait contained in the water may be
accurately afcertained.

§ VIII. Concerning Artificial Mineral

Waters.

The numerous proceffes we have defcribed
for examining the refidues of mineral waters

by evaporation, ferve to afcertain with the
greateft precifion all the feveral matters held
in folution in thefe fluids. Another pro*
cefs remains to be made to prove the fuccefs
of the analyfis, viz. That of imitating na-
ture in the way of fynthefis, by diffolving
pure water the different fuhftances, obtained
by the analyfis of a mineral water which
has been examined. If the artificial mine-
ral water has the fame tafte, the fame weight*
and exhibits the fame phenomena with re-
agents as the natural mineral water, it is
the moft complete, and the moft certain
proof that the analyfis has been well made.
This artificial combination has likewife the
advantage of being procured in all places at
pleafure, and at a trifling expenee ^ and is
even in fome cafes fuperior to the natural
mineral waters, whofe properties may be
changed by carriage, and other circumftan-
ces. The moft celebrated chemifts are of
opinion, that it is poflible to imitate mi-
neral waters. Macquer has obferved, that
fincc the difcovery of the cretaceous acid,
and the property it is found to poffefs of
rendering many fubftances foluble in water,
it is much more eafy to prepare artificial
mineral waters. Bergman has defcribedthe
method of compofing waters, which per-
fectly imitate thofe of Spa, Seltzer, Pyr-
mont, &c. He likewife informs us, that
they are ufed with great fucceis in Sweden,
Vol. III. K k and

£06 MINERAL WATERS.

and that he himfelf has experienced their
good effe&s. M. Duchanoy has publifhed
a work, in which he has given a number of
procefles for imitating all the mineral waters
ufually employed in medicine. We may
therefore hope, that chemiftry may render
the moft effential fervice to the art of heal-
ing, by affording valuable medicines, whofe
a&ivity may be increafed or diminifhed at
pleafure.

End or Volume the third*

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